Implantable Drug Delivery Device and Methods for Treatment of the Bladder and Other Body Vesicles or Lumens

ABSTRACT

An implantable medical device is provided for controlled drug delivery within the bladder, or other body vesicle. The device may include at least one drug reservoir component comprising a drug; and a vesicle retention frame which comprises an elastic wire having a first end, an opposing second end, and an intermediate region therebetween, wherein the drug reservoir component is attached to the intermediate region of the vesicle retention frame. The retention frame prevents accidental voiding of the device from the bladder, and it preferably has a spring constant selected for the device to effectively stay in the bladder during urination while minimizing the irritation of the bladder.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional Application No.61/007,177, filed Dec. 11, 2007, and U.S. Provisional Application No.61/084,927, filed Jul. 30, 2008, each of which is incorporated byreference in its entirety.

BACKGROUND OF THE INVENTION

This invention is generally in the field of implantable drug deliverydevices, and more particularly in the field of devices for thecontrolled release of a drug from a device implantable in the bladder orother body lumen or cavity.

Drug delivery is an important aspect of medical treatment. The efficacyof many drugs is directly related to the way in which they areadministered. Various systemic methods of drug delivery include oral,intravenous, intramuscular, and transdermal. These systemic methods mayproduce undesirable side effects and may result in the metabolization ofthe drug by physiological processes, ultimately reducing the quantity ofdrug to reach the desired site. Accordingly, a variety of devices andmethods have been developed to deliver drug in a more targeted manner.For example, these devices and methods may deliver the drug locally,which may address many of the problems associated with systemic drugdelivery.

In recent years, the development of microdevices for local drug deliveryis one area that has proceeded steadily. Activation of drug release canbe passively or actively controlled. Examples of controlled drugdelivery devices are disclosed in U.S. Pat. No. 5,797,898, U.S. Pat. No.6,730,072, U.S. Pat. No. 6,808,522, and U.S. Pat. No. 6,875,208.

These microdevices can be divided roughly in two categories: resorbablepolymer-based devices and nonresorbable devices. Polymer devices havethe potential for being biodegradable, therefore avoiding the need forremoval after implantation. These devices typically have been designedto provide controlled release of drug in vivo by diffusion of the drugout of the polymer and/or by degradation of the polymer over apredetermined period following administration to the patient.

Interstitial cystitis (IC) and chronic prostatitis/chronic pelvic painsyndrome (CP/CPPS) are chronic painful disorders that affectapproximately 67 per 100,000 women (Curhan et al., J. Urol. 161(2):549-52 (1999)) and 7 per 100,000 men (Collins et al., J. Urol. 159(4):1224-28 (1998)) in the United States. Both conditions are characterizedby chronic pelvic pain, urinary frequency and urgency, and variabledegrees of sexual dysfunction. Pentosan polysulfate sodium (PPS)currently is used to treat this condition. However, conventional methodsand devices for delivering the drug have significant shortcomings. Forexamples oral delivery (ELMIRON™, Ortho-McNeil) suffers from lowbioavailability, as low as 3% due to a high first pass effect (Parsonset al., J. Urol. 153(1) 139-42 (1990)), and causes some mild sideeffects, such as headaches. PPS delivered intravesically throughcystoscopy (with a catheter through the urethra) can provide improvedtherapeutic effects while reducing the side effects of the drug (Bade etal., Br. J. Urol. 79(2): 168-71 (1997)). However, the instillationprocedure is painful and requires repeating the procedure twice per weekfor three months. The repetitive nature of this procedure also engendershigh risks for urinary tract infection and bacteremia. Thus, apronounced need exists for an intravesical drug delivery device thatwill substantially reduce the number of cystoscopic procedures necessaryto deliver an effective amount of PPS or other drugs needed for localdelivery over an extended period.

One treatment for IC/PBS entails delivering a lidocaine solution to thebladder via instillation (R. Henry, et al., “Absorption of alkalizedintravesical lidocaine in normal and inflamed bladders: a simple methodfor improving bladder anesthesia,” J Urol, 165:1900-03, 2001; C. L.Parsons, “Successful downregulation of bladder sensory nerves withcombination of heparin and alkalinized lidocaine in patients withinterstitial cystitis,” Urology, 65:45-48, 2005). The bladder lining hassuch a strong mucous barrier that normal lidocaine has difficultycrossing through it. However, researchers found that if the anestheticagent is alkalinized with a precise amount of sodium bicarbonate, itimproved the anesthetic agent's ability to pass through the mucous toreach and soothe the irritated nerves and tissues beneath. In aconventional procedure, the instillation delivers a bolus dose oflidocaine (or marcaine), heparin, and sodium bicarbonate to the bladder.Over the relatively short time that the solution is present in thebladder, the bladder tissue absorbs the lidocaine to provide the patientwith immediate relief from pain and urgency. The absorbed lidocaine alsoprovides continued relief as the lidocaine degrades from the bladdertissue. However, lidocaine has a relatively short half life, andtherefore a relatively high initial concentration of lidocaine may beneeded to provide continued relief and the period of relief limited induration. To achieve sustained relief, subsequent instillations may berequired, such as three times per week for two weeks. The frequency ofsuch instillations may be undesirable, as each instillation entails theinconvenience, discomfort, and risk of infection associated with urinarycatheterization. The duration of relief may be increased by increasingthe initial concentration of lidocaine absorbed into the bladder, suchas by increasing the concentration in the solution. However, undesirablesystemic effects may result if the initial concentration of lidocaine istoo high.

Other therapies could benefit from improved intravesical drug deliverydevices, particularly where local delivery of a drug to the bladder ispreferred or necessary—such as when the side effects associated withsystemic delivery of the drug are unbearable and/or when bioavailabilityfrom oral administration is too low. For instance, oxybutynin is usedfor the treatment of overactive bladder syndrome. Currently, oxybutyninis delivered orally or transdermally. Unfortunately, however,approximately 61% of patients taking the drug experience side effectsand approximately 7 to 11% of the patients actually stop treatment dueto the severity of the side effects.

Situs Corporation developed an intravesical drug delivery system (UROSinfuser device) for the delivery of pharmaceutical solutions of drugs,such as oxybutynin (for the treatment of overactive bladder) andmitomycin C (for the treatment of bladder cancer). The UROS infuserdevice and methods of making and implanting the device are described inU.S. Pat. No. 6,171,298, U.S. Pat. No. 6,183,461, and U.S. Pat. No.6,139,535. The UROS infuser device has an elastomeric outer tubing andcontains inextensible wire which connects both inner ends. The devicehas a linear shape during the cystoscopic insertion into the bladder,changes to a crescent shape following implantation and filling of thedevice with the pharmaceutical solution, and returns to a linear shapeafter releasing all of the pharmaceutical solution. Extended release ofthe pharmaceutical solution is controlled by means of apressure-responsive valve and/or flow-resistive element inside thetubing. The size of the UROS infuser device depends on the size of eachinner component, and a considerable portion of the inner volume is usedto contain the mechanical components, not drug solution. With a lengthof approximately 10 cm and an outer diameter of approximately 0.6 cm,the large size of the UROS infuser device can cause significantdiscomfort and pain to patients, particularly during urologicaldeployment and retrieval of the device. The UROS infuser device alsorequires an additional surgical procedure for loading of thepharmaceutical solution into the device following implantation.Accordingly, a need exists for an intravesical drug delivery device thatis smaller in size, to avoid unnecessary discomfort and pain inpatients. In addition, it would be desirable to provide an intravesicaldrug delivery device that can minimize the number of surgical proceduresrequired for implantation and delivery of drug over the treatmentperiod.

There is also a need to provide sustained delivery over a period oftime, and, to accomplish this in the bladder, the device desirablyshould be retained in the bladder and not excreted before the drugpayload can be at least substantially released, even when the drugpayload needs to be delivered over a period of several days or weeks. Ingeneral, better devices are needed for controlled delivery of drug tothe bladder. Desirably, the implantable device should be easy to deliverinto (and if necessary, remove from) the bladder with minimum pain ordiscomfort to the patient.

SUMMARY OF THE INVENTION

In one aspect, an implantable medical device is provided for controlleddrug delivery within the bladder, or other body vesicle. In oneembodiment, the device includes at least one drug reservoir componentcomprising a drug; and a vesicle retention frame which comprises anelastic wire having a first end, an opposing second end, and anintermediate region therebetween, wherein the drug reservoir componentis attached to the intermediate region of the vesicle retention frame.The retention frame has been determined to be crucial to preventaccidental voiding of the device from the bladder. It preferably has aspring constant selected for the device to effectively stay in thebladder during urination while minimizing the irritation of the bladder.

In one embodiment, the elastic wire may include or consist of a lowmodulus elastomer, such as silicone, polyurethane, styrenicthermoplastic elastomer, poly(glycerol-sebacate), or a combinationthereof. In another embodiment, the elastic wire may include or consistof a superelastic alloy or other shape memory material. For example, thesuperelastic alloy may comprise a biocompatible nickel-titanium alloy(e.g., Nitinol) or a titanium-molybdenum alloy (e.g., Flexium). In oneembodiment, the elastic wire may have a biocompatible polymeric coating,such as silicone, polyurethane, styrenic thermoplastic elastomer,Silitek, Tecoflex, C-flex, and Percuflex.

In one embodiment, the elastic wire in its uncompressed state may be ina curled form, for example, in the form of two or more loops, spirals,or turns. The first and second ends of the elastic wire may be boundedwithin said one or more loops. The first and second ends of the elasticwire preferably are soft and blunt. The elastic wire in its uncompressedstate may be curled in the form of two or more loops, such that the wirecan be uncurled into an approximately linear shape to permit the deviceto be passed through a lumen of a catheter sized for insertion throughthe urethra of a patient.

In one embodiment, the drug reservoir component includes at least oneelongated elastomeric tube having a first end portion and an opposingsecond end portion and comprising a drug formulation therein, the tubebeing operable to dispense the drug in vivo at a controlled rate. In oneembodiment, the tube is formed of a water permeable material, such as asilicone. In one embodiment, the tube may be formed of a resorbablematerial. In a preferred embodiment, the tube is formed of a materialwhich comprises or consists of a biocompatible, low modulus elastomer.

A drug formulation may be positioned as a core within the tube. The drugmay be dispensed from the device, i.e., released from the tube in vivo(e.g., within the bladder), at a controlled rate by osmosis and/or bydiffusion. In one embodiment, the tube may have no aperture, and thedrug may, depending on its molecular size and/or structure, diffusethrough the tube. In one embodiment, the tube may include one or moreapertures, and the drug may be released at a rate controlled by osmosis.In an embodiment, the drug is dispensed at a rate controlled at least inpart by diffusion and/or resorption or dissolution of a matrix material,e.g., wherein the tube comprises a composite, such as a polymer/drugcomposite. The drug formulation preferably is in a solid or semi-solidform. This may facilitate loading the required dosage in a relativelysmall volume, to minimize undue irritation and discomfort to the patientduring and following implantation of the device.

The device may include at least one magnetic element to facilitatecytoscopic withdrawal of the device from the bladder, e.g., after drugdelivery has been completed. In certain embodiments, the magneticelement may be located at the first end, the second end, or both thefirst and second ends of the vesicle retention frame. A soft polymericcoating may be provided over the magnetic elements.

In an alternative embodiment, the device may be formed of resorbablematerials such that retrieval of the device is unnecessary, in that itwill degrade completely or at least enough to void the remnants of thedevice.

The aperture(s) for release of the drug are, in at least a preferredembodiment, within a size range where release is controlled osmotically.In one embodiment, the aperture is circular and has a diameter betweenabout 25 μm and about 500 μm. Drug release may occur too quickly if theaperture is too large, and it was found that hydraulic pressure maydeform the drug reservoir tubing and possibly alter the aperture, if theaperture size is too small.

The device may further include a floatation feature by the use of lowdensity materials and/or the inclusion of air or another gas in somepart of the device. The floatation feature may minimize the possibleirritation of the trigone of the urinary bladder. The device also mayinclude, e.g., embedded, radioopaque materials for possible x-raymonitoring of the device.

The size of the tubing lumen of the drug reservoir component determinesthe possible drug payload volume. In one embodiment, the hollow tube ofthe drug reservoir component may have an inner diameter between about0.3 mm and about 2 mm and an outer diameter between about 0.6 mm andabout 3 mm. The length(s) of the tubing between the end seals may vary,as may the number of tubing segments attached to any one retentionframe.

In a particular embodiment, the implantable medical device forcontrolled drug delivery may include at least one drug reservoircomponent which comprises an elongated, water permeable, elastomerictube having a first end and an opposing second end, a solid orsemi-solid drug formulation core within the tube, wherein the tube hasone or more apertures for dispensing the drug at a controlled rate; anda vesicle retention frame which comprises an elastic wire having a firstend, an opposing second end, and an intermediate region therebetween,wherein the elastic wire comprises a superelastic alloy or other shapememory material, or a low modulus elastomer, and the elastomeric tube ofthe drug reservoir component is attached to the vesicle retention frameabout the intermediate region. In a preferred embodiment, theelastomeric tube is formed of a silicone.

In another aspect, a method is provided for administration of a drug toa local tissue site within/adjacent a body lumen of patient, forexample, into a patient's bladder. In one case, the method may compriseproviding a lumen device, such as a urethral catheter or cytoseope,which has a distal end, an opposing proximal end, and an open lumenextending therebetween; inserting the distal end of the urethralcatheter into the bladder of a patient in need of treatment, where theproximal end of the urethral catheter remains outside of the patient;deforming (e.g., uncurling) the implantable drug delivery device andpassing it into the proximal end of the lumen of the urethral catheter;driving the deformed device through the lumen and out of the lumen,whereupon the device returns to its undeformed shape for retention inthe bladder; and removing the urethral catheter from the patient.Thereafter, the drug is released in a controlled manner from the drugreservoir component of the device. In certain embodiments of thismethod, the patient may be in need of treatment for interstitialcystitis, overactive bladder syndrome, or bladder cancer.

In still another aspect, a method of treatment of the bladder in apatient is provided. In one embodiment the method comprises implantingwholly within the patient's bladder a drug release device; andcontrollably releasing a local anesthetic agent from the drug deliverydevice in a manner providing a sustained, therapeutically effectiveconcentration of the anesthetic agent in the urothelium of the bladder,while avoiding high peak plasma concentrations of the anesthetic agent.The anesthetic agent may be lidocaine. In one embodiment, theconcentration of the anesthetic agent in the urothelium is at least 1000times higher than the plasma concentration. In one embodiment, thetherapeutically effective concentration of the anesthetic agent in theurothelium is sustained for between 1 and 30 days.

In yet another aspect, a method is provided for treatment of the bladderin a patient, in which the method includes implanting wholly within thepatient's bladder a drug release device; and controllably releasing adrug from the drug delivery device in a manner providing a sustained,therapeutically effective concentration of the drug in the urothelium ofthe bladder, while avoiding high peak plasma concentrations of theanesthetic agent, wherein the drug has a half-life that is equivalent toor within 25% of that of lidocaine.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a plan view of an embodiment of a drug delivery device in arelatively expanded shape.

FIG. 2 is a plan view of the embodiment of the drug delivery deviceshown in FIG. 1, illustrating the drug delivery device in a relativelylower profile shape inside of a catheter.

FIG. 3 illustrates an embodiment of a drug reservoir portion of the drugdelivery device, wherein FIG. 3A is a side view, FIG. 3B is across-sectional view, and FIG. 3C is a cross-sectional view.

FIG. 4 is a cross-sectional view of an embodiment of a drug reservoirportion that includes multiple reservoirs separated by partitionstructures.

FIG. 5 is a cross-sectional view of an embodiment of a drug reservoirportion having an orifice structure at one end and an aperture formedthrough the orifice structure.

FIG. 6 illustrates example shapes for a vesicle retention frame portionof the drug delivery device, the shapes including one or more loops,curls, or sub-circles.

FIG. 7 illustrates example shapes for the frame that include one or morecircles or ovals arranged in a two-dimensional or a three-dimensionalconfiguration.

FIG. 8 illustrates examples embodiments of a pretzel shaped retentionframe having one or more drug reservoirs attached at an intermediateregion of the retention frame.

FIG. 9 shows another embodiment of a retention frame having a number ofdrug reservoir portions attached at an intermediate region of theretention frame, with FIG. 9A illustrating the device shown in arelatively expanded shape and FIG. 9B illustrating the device in arelatively lower profile shape within a catheter.

FIG. 10 illustrates cross-sectional views of example embodiments of adrug delivery device having a drug reservoir portion substantiallyaligned with a retention frame.

FIG. 11 illustrates cross-sectional views of example embodiments of adrug delivery device having a number of drug reservoir portionssubstantially aligned with a retention frame.

FIG. 12 illustrates an embodiment of a drug delivery device wherein aretention frame component extends through a portion of a drug reservoircomponent to attach the two components together.

FIG. 13 is a side view of an embodiment of a drug delivery device,illustrating rate controlling coatings or sheaths positioned near arelease aperture, with interior components of the device beingillustrated with cross-hatching.

FIG. 14 is a block diagram illustrating an embodiment of a method ofmaking an implantable drug delivery device.

FIG. 15 illustrates a method of implanting an intravesical drug deliverydevice.

FIG. 16 is a block diagram illustrating a method of delivering lidocaineto the bladder.

FIG. 17 illustrates cross-sectional views of three different embodimentsof a drug delivery device.

FIG. 18 is a graph illustrating in vitro drug release profiles for thethree embodiments of the drug delivery device shown in FIG. 17.

FIG. 19 illustrates an embodiment of a pretzel shaped retention frame,at three different points during a compression test wherein acompressive force was applied to the frame.

FIG. 20 is a graph illustrating force and displacement data collectedduring the compression test performed on the device shown in FIG. 19.

FIG. 21 is a graph illustrating the release of lidocaine over timeexhibited in vitro by various implantable drug delivery devices.

FIG. 22 is a graph illustrating lidocaine plasma concentration over timeexhibited for various instillations and implanted devices in vivo inrabbit bladder.

FIG. 23 a graph illustrating lidocaine plasma concentration over time,exhibited for various instillations and implanted devices in vivo inrabbit bladder, with the y-axis modified.

FIG. 24 is a graph illustrating the lidocaine tissue concentration overtime, exhibited for various implanted devices in vivo in rabbit bladder.

FIG. 25 is a graph illustrating the correlation between lidocaine tissueconcentration and lidocaine plasma concentration, exhibited for variousinstillations and implanted devices in vivo in rabbit bladder.

FIG. 26 is a graph illustrating lidocaine concentration in tissue andurine, exhibited by devices implanted in vivo in rabbit bladder forthree days and for six days.

FIG. 27 is a graph illustrating the effect of pH on the absorption oflidocaine, exhibited during studies performed in vitro on rat bladderfor one hour and for one day, respectively.

FIG. 28 is a graph illustrating lidocaine tissue concentration overtime, exhibited during studies performed in vitro on rat bladder with10⁻⁵% and 1% lidocaine solutions of varying pH.

DETAILED DESCRIPTION OF THE INVENTION

Improved drug delivery devices are provided for implantation andretention in the bladder or other body vesicles or lumens. The devicecan be tailored to release one or more drugs over an extended period oftime in a predefined manner, for therapies requiring bolus (one-time),pulsatile, or constant drug delivery.

Importantly, the implantable device is designed for retention within thebody, such as within the bladder. That is, the device is designed toresist excretion, such as in response to the forces associated withurination. For example, the device may include a retention frame. Theretention frame may be configured into a relatively low profile fordeployment into the body, and once implanted may assume a relativelyexpanded profile to facilitate retention. The device may be highlyflexible, so that the drug-loaded device can easily be deformed, such asfrom a coiled shape to a straightened shape, to permit deploymentthrough a lumen of a catheter into the bladder.

The device may be non-surgically implanted, such as through a cytoscope,and the device may continue delivering a drug long after the cytoscopeis removed. In contrast to an indwelling catheter, which may act as apath for bacteria to migrate into the bladder, the implanted deviceadvantageously is able to be located entirely within the bladder. Thus,the opportunity for infection is greatly diminished with the presentdevice.

Regarding the bladder specifically, the device also advantageouslyaddresses many of the deficiencies of conventional treatment options,such as drug delivery via instillation, systemic drug delivery, and drugdelivery via devices cystoscopically implanted in the bladder. Thepresent device can be implanted once and can release the drug over anextended period, without requiring surgery or frequent interventions(such as to re-fill the drug reservoir of a conventional device). Bylimiting the number of procedures required to be performed on thepatient during the treatment process, the present local drug deliverysystem can improve the quality of life of the patient during thetreatment process. The drug delivery device can also avoid potentialside effects associated with systemic administration of the drug whileincreasing the amount of drug delivered locally to the bladder.

In one embodiment, the drug delivery device may permit deliveringlidocaine (or another cocaine analogue) locally to the bladder over arelatively extended period of time. Thus, the device may provide abeneficial alternative to frequent intravesical instillations of alidocaine solution for the treatment of IC/PBS. The device may be apassive, non-resorbable device that may be deployed and retrieved by aconventional catheterization, a simple non-surgical outpatientprocedure. Unlike intravesical instillation, which loads the bladderwith a relatively high concentration of lidocaine over a relativelyshort time span, the present device may permit continuously releasing arelatively lower level of lidocaine over a relatively longer time span.Thus, the patient may experience sustained relief from the symptoms ofIC/PBS without receiving a high initial concentration of lidocaine andwithout experiencing the discomfort and inconvenience of repeatedintravesical installations. Further, it is not necessary to deliver thelidocaine in an alkaline solution in order to achieve effective bladdertissue concentrations.

I. The Implantable Drug Delivery Device

In embodiments, the drug delivery device may include two primary partsor portions: the drug reservoir portion and the vesicle retention frameportion. The drug reservoir portion may be referred to herein as the“device body” and may hold the drug to be delivered into the body. Theretention frame portion may be associated with the drug reservoirportion and may facilitate retaining the device in the body. FIG. 1illustrates an example embodiment of the device 10, the device havingboth a drug reservoir portion 12 and a retention frame portion 14. Inembodiments in which the device is designed for implantation in thebladder, the retention frame portion may impede accidental voiding ofthe device, and thus the drug reservoir portion, from the bladder.

More specifically, the drug delivery device may be elasticallydeformable between a relatively expanded shape and a relatively lowerprofile shape. The relatively lower profile shape may be suited forinserting the drug delivery device into the body. For example, therelatively lower profile shape may be suited for inserting the drugdelivery device through a catheter into a cavity of the body, such asthrough a urethral catheter into the bladder. An example in shown inFIG. 2, which illustrates the device 10 of FIG. 1 in a channel 20, suchas a working channel of a cystoscope or other catheter. In suchembodiments, the relatively lower profile shape may be a relativelytubular, elongated, or linear shape, such as the shape shown in FIG. 2,so that the device may pass through the catheter. Following passage intothe body, the device may assume the relatively expanded shape, such asthe shape shown in FIG. 1, which may facilitate retention of the drugdelivery device in the body cavity.

In embodiments, the drug delivery device may naturally assume therelatively expanded shape. The device may be elastically deformed intothe relatively lower profile shape for insertion into the body, and thedevice may spontaneously or naturally return to the initial, relativelyexpanded shape once implanted for retention within the body.

The retention frame may have a certain elastic limit and modulus thatallows the device to be introduced into the body in a relatively lowerprofile shape but then permits the device to return the relativelyexpanded shape once inside the body. The device may also have asufficient elastic modulus to impede the device from assuming therelatively lower profile shape once implanted, so as to limit or preventaccidentally expulsion of the device from the body under expectedforces. For example, the characteristics of the retention frame may beselected to facilitate retaining the device in the relatively expandedshape despite expected forces in the bladder, such as the hydrodynamicforces associated with urination or contraction of the detrusor muscle.Thus, expulsion from the bladder is impeded or prevented.

In embodiments in which the drug delivery device is designed to beimplanted in the bladder, the drug delivery device may be designed to beinserted into and retrieved from the bladder through the urethracystoscopically. Thus, the device may be sized and shaped to fit througha narrow tubular path of a cytoscope. Typically, a cytoscope for anadult human has an outer diameter of about 5 mm and a working channelhaving a diameter of about 2.4 mm. Thus, the device may be relativelysmall in size. For example, when the device is elastically deformed tothe relatively lower profile shape, the device may have a total outerdiameter that is less than about 2.4 mm, such as between about 2.0 mmand about 2.3 mm.

In addition to permitting insertion, the relatively small size of thedevice may also reduce patient discomfort and trauma to the bladder. Forexample, the relatively small size of the device may reduce irritationof the bladder trigone, which is responsible for creating the sensationof urgency of urination. The device may also have a density that is lessthan the density of urine or water, so that the device may float insidethe bladder. Such floatation, although not required, may prevent thedevice from touching the sensitive trigone region of the bladder nearthe bladder neck. For example, the device may be formed from relativelylow density materials of construction, or air or other gas may beentrapped in the device. The outer surface of the device, furthermore,may be soft and smooth without sharp edges or tips.

The exact configuration and shape of the intravesical drug deliverydevice may be selected depending upon a variety of factors including thespecific site of implantation, route of implantation, drug, dosageregimen, and therapeutic application of the device. Preferably, thedesign of the device will minimize the patient's pain and discomfort,while delivering a therapeutically effective dose of the drug locally tothe patient.

The intravesical drug delivery device can be made to be completely orpartially resorbable so that no explantation of the device is requiredfollowing release of the drug formulation. As used herein, the term“resorbable” means that the device, or part thereof, degrades in vivo bydissolution, enzymatic hydrolysis, erosion, or a combination thereof.This degradation occurs at a time that does not interfere with theintended kinetics of release of the drug from the device. For example,substantial resorption of the device may not occur until after the drugformulation is substantially or completely released. Alternatively, theintravesical drug delivery device may be at least partiallynon-resorbable, such that the device may be removed following release ofthe drug formulation. In such embodiments, the device may not becompletely resorbable; for example, the device may be partiallyresorbable so that the device, upon partial resorption, breaks intonon-resorbable pieces small enough to be excreted from the bladder.Useful biocompatible resorbable and non-resorbable materials ofconstruction are known in the art. In embodiments, the device may beformed from materials suited for urological applications, such asmedical grade silicone, natural latex, PTFE, ePTFE, stainless steel,nitinol, elgiloy (non ferro magnetic metal alloy), polypropylene,polyethylene, polycarbonate, polyester, nylon, or combinations thereof.

The Drug Reservoir Portion

The drug reservoir portion of the device may include an elongated tube.The tube may have a first end and an opposing second end. An interior ofthe tube may define a reservoir, and a drug formulation core may behoused in the reservoir. The drug formulation may be in a substantiallysolid form, such as a drug rod, although other configurations arepossible. The tube may have one or more apertures for dispensing thedrug, such as via osmosis, diffusion, or a combination thereof amongothers. In embodiments, the release rate of the drug from the drugreservoir portion may be controlled. For example, a degradable membranemay be disposed over or in one or more of the apertures to control theinitiation of release of the drug formulation from the reservoir. Asanother example, a sheath may be positioned over a portion of the tubeto reduce the release rate, such as by reducing the osmotic surface areaof the tube or by reducing diffusion through the tube wall. Also, thedrug reservoir portion may be formed from a drug polymer compositedesigned to release at a known rate.

An example of such a drug reservoir portion is shown in FIGS. 3A-3C. Asshown the drug reservoir portion generally includes a body formed froman elastomeric tube 30. The tube 30 defines a reservoir 32 that containsa drug rod 34. Ends of the tube 30 may be sealed with sealing structures35, further described below. An array of apertures 36 may be disposed inthe tube 30 closed off by degradable timing membranes 38.

In a preferred embodiment, the drug reservoir portion operates as anosmotic pump. In such embodiments, the tube may be formed from a waterpermeable material, such as a silicone. Following implantation, water orurine permeates through the wall of the tube, enters the reservoir, andis imbibed by the drug formulation. Solubilized drug is dispensed at acontrolled rate out of the reservoir through the one or more apertures,driven by osmotic pressure in the reservoir. The delivery rate isaffected by the surface area of the tube, the thickness of the tubewall, the permeability to liquid of the material used to form the tube,and the shape, size, number and placement of the apertures, amongothers. The delivery rate can be predicted from the physicochemicalparameters defining the particular drug delivery system, according towell known principles, which are described for example in Theeuwes, J.Pharm. Sci., 64(12):1987-91 (1975). Example osmotic pump designs, andequations for such selecting such designs, are described below withreference to Examples 1-3.

In an alternative embodiment, the device may operate essentially bydiffusion of the drug from the tube through, for example, one or more ofthe apertures, the wall of the tube, or a combination thereof. In stillother embodiments, the device may operate by a combination of osmosisand diffusion.

In embodiments, the drug reservoir portion may be formed from anelastomeric material, which may permit elastically deforming the devicefor insertion. For example, the tube may be elastically deformed alongwith the vesicle retention frame for intravesical implantation, asdescribed in further detail below.

In embodiments, the drug reservoir portion may be made of abiocompatible, water permeable material known in the art, which maypermit releasing the drug from the reservoir via osmosis. The drugreservoir portion alternatively may be substantially water impermeable.

In embodiments, the drug reservoir portion may be formed from a materialthat is both elastomeric and water permeable. An example material issilicone that is both elastomeric and water permeable, although otherbiocompatible materials may be used.

The length, diameter, and thickness of the tube may be selected based onthe volume of drug formulation to be contained, the desired rate ofdelivery of the drug from the tube, the intended site of implantation ofthe device within the body, the desired mechanical integrity for thedevice, the desired release rate or permeability to water and urine, andthe desired method or route of insertion into the body, among others. Inembodiments, the drug reservoir portion has a length in the range ofabout 1 cm to about 10 cm, an inner diameter in the range of about 0.3mm to about 2 mm, and an outer diameter in the range of about 0.6 mm andabout 3 mm.

In one embodiment, the device body is non-resorbable. It may be formedof a medical grade silicone tubing, as known in the art. Other examplesof suitable non-resorbable materials include synthetic polymers selectedfrom poly(ethers), poly(acrylates), poly(methacrylates), poly(vinylpyrolidones), poly(vinyl acetates), poly(urethanes), celluloses,cellulose acetates, poly(siloxanes), poly(ethylene),poly(tetrafluoroethylene) and other fluorinated polymers,poly(siloxanes), copolymers thereof, and combinations thereof.

In another embodiment, the device body is resorbable. In one embodimentof a resorbable device, the tube of the body is formed of abiodegradable or bioerodible polymer. Examples of suitable resorbablematerials include synthetic polymers selected from poly(amides),poly(esters), poly(ester amides), poly(anhydrides), poly(orthoesters),polyphosphazenes, pseudo poly(amino acids), poly(glycerol-sebacate),copolymers thereof, and mixtures thereof. In a preferred embodiment, theresorbable synthetic polymers are selected from poly(lactic acids),poly(glycolic acids), poly(lactic-co-glycolic acids),poly(caprolactones), and mixtures thereof. Other curable bioresorbableelastomers include poly(caprolactone) (PC) derivatives, aminoalcohol-based poly(ester amides) (PEA) and poly (octane-diol citrate)(POC). PC-based polymers may require additional cross-linking agentssuch as lysine diisocyanate or 2,2-bis(-caprolacton-4-yl)propane toobtain elastomeric properties.

The drug reservoir portion may be made as described in U.S. PatentApplication Publication No. 2007/0202151 to Lee et al., which isincorporated herein by reference.

As mentioned, the tube may be hollow, so that the drug reservoir isdefined therein. For example, the tube may be substantially linear, suchas substantially cylindrical in shape. Thus, the tube may have acircular cross-section; however, other cross-sectional shapes of thetube are envisioned, such as square, triangle, hexagon, and otherpolygons, among others. The ends of the tube may be sealed to limitescape of the drug. For example, each end of the tube may be closed offusing, a sealing structure, a medical grade silicone adhesive, othersealing means known in the art, or combinations thereof. In embodimentsin which the tube is sealed with a sealing structure, the sealingstructure may be a ball, a disk, or any other shape suited to plug,close, the end of the tube. An embodiment of a ball-shaped sealingstructure 35 in shown in FIG. 3B. Such a sealing structure may be formedfrom a material a biocompatible metallic material such as stainlesssteel or a biocompatible polymeric material, such as a biodegradable orbioerodible polymer, although other materials may be used. The sealingstructure may have a relatively larger diameter than the inner diameterof the tube, such that the tube stretches to fit snugly about thesealing structure.

In one embodiment, the tube has multiple reservoirs. Multiple aperturesmay either share a common drug reservoir or have separate reservoirs.Such a multi-reservoir device is useful in at least two particular typesof device embodiments: (1) when two or more separate drug formulationsare to be delivered from a single device, or (2) when a single drug isto be delivered at two different rates or at different times followingimplantation, such as when a first dose of the drug is pre-programmed torelease at a first time and a second dose is pre-programmed to releaseat a second, later time. This different pre-programming can be achievedby using different timing membranes for the different reservoirs, forinstance with two or more reservoirs, the reservoirs being defined bythe inner surface of the tube and at least one partition. The partitionstructure in the tube may be in the form of a spheroidal object, such asa ceramic bead or other microsphere. The partition structure also may bein the shape of a disk or cylinder. Other configurations are alsopossible. The partition may be non-resorbable or resorbable. In oneembodiment, the partition structure may be made of a biocompatiblepolymeric material, such as a biodegradable or bioerodible polymer.

An embodiment of such a drug reservoir portion is shown in FIG. 4. Thedrug reservoir portion has a body that includes a linear tube 40. Thehollow space in the tube 40 is partitioned into three reservoirs 42 a,42 b, 42 c, each of which has a single corresponding aperture 44 a, 44b, 44 c. The reservoirs 42 are defined by the inner surface of the tube40, meaning the sidewall of the tube, and by spherical partitionstructures 46 a, 46 b, 46 c and 46 d spaced within the interior space ofthe tube. As can be seen, the partition structures are secured in placewithin the tube 40 by having a larger diameter than the inner diameterof the unstretched elastomeric tube, which causes the tube to stretchand snugly fit around the partition structures, sealing each reservoir.

In embodiments, partitioned reservoirs may prevent an aperture with afaster biodegradable membrane from monopolizing the release of theloaded drug material, potentially leaving little or no drug material forrelease from apertures with subsequently degrading membranes. Providinga separate reservoir for each release aperture may increase the effectof multiple biodegradable timing membranes.

In a preferred embodiment, the total volume of the reservoir (orcombined reservoirs) is sufficient to contain all the drug needed forlocal delivery over the course of a single therapy. That is, the drugreservoir portion desirably contains all of the doses of druganticipated, so that multiple cystoscopic procedures are not needed, orare reduced in number/frequency to complete the therapy prescribed for agiven disease or condition.

Apertures

In one embodiment, the device body includes one or more apertures ororifices through the sidewall or end of the tube. The one or moreapertures provide a passageway to release the drug formulation from thedrug delivery device. In one embodiment, the device includes an array oftwo or more discrete apertures in spaced positions in the tube. The twoor more apertures may be in fluid communication with a single reservoiror with a plurality of reservoirs. The placement of apertures near theportion of the tube which will be folded during cystoscopic insertionmay be avoided in order to prevent the possible tear of polymerbiodegradable membranes on the apertures. Embodiments of apertures 36are shown on the tube 30 of the drug reservoir portion shown in FIG. 3A.

The size of the aperture may be selected to provide a controlled rate ofrelease of the drug. In embodiments in which the device is intended tooperate primarily as an osmotic pump, the size of the aperture may beselected such that the aperture is small enough to minimize or otherwisereduce diffusion of the drug through the aperture. The apertures mayalso be configured to prevent excessive buildup of hydrostatic pressurein the tube, which may increase the volume of fluid in the reservoir,resulting in swelling of tube. For example, an increase in hydrostaticpressure within the reservoir may be prevented by the ensuring the sizeof the aperture is large enough and/or by spacing a number of aperturesalong the length of the tube. Within these constraints on aperture sizeand number, one may then vary the size and number of such aperturesemployed in a single device (or in a single reservoir) in order toprovide a needed total rate of drug released. In exemplary embodiments,the diameter of the aperture is between about 20 μm and about 300 μm(e.g., 20 to 100 μm, 25 to 75 μm, etc.). In one example, the aperture iscircular and has a diameter between about 25 μm and about 500 μm. Inanother example, the aperture is circular and has a diameter betweenabout 20 μm and about 75 μm. In one particular example, the aperture hasa diameter of about 50 μm. In embodiments where the device operatesprimarily by diffusion, the apertures may be in this range or larger.

A single device may have apertures of two or more different sizes. Theaperture typically is circular in shape, although other shapes arepossible and envisioned, and will typically depend on manufacturingconsiderations.

In one embodiment, the apertures are drilled by laser ablation throughthe wall of the tube, such as the silicone tube. For example, theaperture may be generated using an ultraviolet excimer lasermicromachining system. In such embodiments, the aperture may be slightlytapered from an exterior of the tube to an interior of the tube. Forexample, the aperture may have a diameter of about 55 μm along the outersurface of the tube wall, and the aperture may have a diameter of about45 μm along the inner surface of the tube wall, although any otherconfiguration is possible. The apertures may then be covered withbiodegradable timing membranes. A person of skill may be able to uselaser ablation to drill in a medical grade polymer, via eitherthrough-hole drilling or depth-controlled drilling, to create awell-defined hole with a diameter as small as 0.050 mm. Therefore, theapertures may be created before or after the drug is loaded into thetube.

In another embodiment, one or more apertures may be formed in an orificestructure disposed in an end of the tube. Such an embodiment is shown inFIG. 5. The drug reservoir portion may have a tubular silicone body 50with a precision orifice structure 52 plugging one end of the centralbore of the body. The orifice structure 52 may include an aperture 54. Asealing structure, such as a microbead 56, may plug the opposing end ofthe tube, and a drug formulation 58 may be disposed in the reservoirdefined between the orifice structure 52 and the microbead 56. Theorifice structure may be a precision orifice known in the art (availablefor example from Bird Precision Orifices, Swiss Jewel Company). Theorifice can be inserted within and/or attached to the silicone tubingwith silicone adhesives. In one example, the device may include siliconetubing having an inner diameter of 305 μm and outer diameter of 635 μm,with a precision orifice structure made of ruby or sapphire and havingan outer diameter of about 1.5 mm or smaller.

Degradable Membranes

In one embodiment, each of the one or more apertures has a degradablemembrane disposed over or in each of the apertures (e.g., in registerwith the aperture), to control the time at which release of the drugformulation begins. In one embodiment, the degradable membrane is in theform of a uniform coating covering the outer surface of the tube of thedevice body. In another embodiment, discrete degradable membranes may beprovided substantially within the aperture. Combinations of two or moredegradable membranes may be used to control release from one aperture.

The thickness of the degradable membrane in a particular system willdepend for example on the chemistry and mechanical properties of thematerial of construction selected for the degradable membrane (whichprimarily govern the rate of degradation), as well as on the desiredtime of delay of drug release for the particular drug delivery device.See, e.g., Richards Grayson, et al., “Molecular release from a polymericmicroreservoir device: Influence of chemistry, polymer swelling, andloading on device performance” Wiley InterScience (6 Apr. 2004);Richards Grayson, et al., “Multi-pulse drug delivery form a resorbablepolymeric microchip device” Nature Materials, Advance Online Publication(19 Oct. 2003); U.S. Pat. No. 6,808,522. In one embodiment, thedegradable membrane has a thickness between about 100 μm and about 200μm, such as between 145 μm and 160 μm.

The membranes may be formed of a biocompatible material. In oneembodiment, the membranes are formed of a resorbable synthetic polymersuch as polyester, a poly(anhydride), or a polycaprolactone. In anotherembodiment, the membranes are formed of a resorbable biological materialsuch as cholesterol, other lipids and fats.

For embodiments of these devices in which it is desired to release drugover a short period of time, the degradable membrane may be fabricatedfrom quickly disintegrating materials including, for example,poly(lactide-co-glycolide) copolymers containing a high glycolidecontent, copolymers of poly(lactones) with fast degradation times,certain poly(anhydrides), hydrogels, oligosaccharides, andpolysaccharides. For applications in which a longer or delayed releasetime is desirable, the degradable membrane may be fabricated frommaterials that take longer to disintegrate, for example, resorbablebiological materials such as cholesterol, other lipids and fats, andlipid bilayers, polymers such as poly(caprolactone) or certainpoly(anhydrides), and PLGA copolymers with high lactic acid content.

In certain embodiments, the degradable membranes permit achievingcomplex release profiles from a single drug delivery device. In oneembodiment, this may be accomplished by having different membranes overdifferent apertures, either to the same reservoir or differentreservoirs. In one case, one of the membranes is formed of a firstmaterial and another of the membranes is formed of a second material,wherein the first material has a different degradation rate in vivocompared to the second material. In another case, one of the membraneshas a first thickness and the other of the membranes has a second,greater thickness. These approaches may be mixed and matched to design aparticular release profile, alone or in combination with kineticsaltering approaches based on formulating the drug with a releasecontrolling excipient material, or covering a portion of the drugreservoir portion with a release altering sheath, as described below.

The Drug Formulation

The drug formulation can include essentially any therapeutic,prophylactic, or diagnostic agent that would be useful to deliverlocally to a body cavity. The drug formulation may consist only of thedrug, or may include one or more pharmaceutically acceptable excipients.

In a preferred embodiment, the drug formulation is in a solid orsemi-solid form in order to reduce the overall volume of the drugformulation and thereby reduce the size of the device—to promote ease ofimplantation. The semi-solid form may be, for example, an emulsion orsuspension; a gel or a paste. In one example, the drug formulation is inthe form of a solid drug rod. Embodiments of drug rods, and methods ofmaking such drug rods, are described in U.S. patent application Ser. No.11/463,956, which is incorporated by reference in its entirety. The drugrods may be formed by adapting other extrusion or casting techniquesknown in the art. For example, a drug rod comprising chondroitin6-sulfate or chondroitin sulfate C may be formed by filling a tube withan aqueous CSC solution and then allowing the solution to evaporate. Asanother example, a drug rod comprising lidocaine may be formed may beformed by filling a tube with an aqueous solution comprising lidocaine,allowing the solution to evaporate, and then crystallizing the resultinggel. In many embodiments, the drug formulation desirably includes no ora minimum quantity of excipient for the same reasons of volume/sizeminimization.

In other embodiments, the drug formulation may be in the form of aliquid, solution, suspension, emulsion, emulsions, colloidalsuspensions, slurries, gel mixtures such as hydrogels, or combinationthereof. The drug formulation may be in a powder or microparticle form,for example, as a hydratable or water soluble solid.

Pharmaceutically acceptable excipients are known in the art and mayinclude viscosity modifiers, bulking agents, surface active agents,dispersants, osmotic agents, diluents, and other non-active ingredientsof the formulation intended to facilitate handling, stability,dispersibility, wettability, and/or release kinetics of the drug (i.e.,the active pharmaceutical ingredient or diagnostic agent).

In a particular embodiment, the intravesical drug delivery device isused to provide pain relief to the patient. A variety of anestheticagent, analgesic agents, and combinations thereof may be used.Representative examples of suitable such agents include lidocainehydrochloride, procaine hydrochloride, salicyl alcohol, tetracainehydrochloride, phenazopyridine hydrochloride, acetaminophen,acetylsalicylic acid, flufenisal, ibuprofen, indoprofen, indomethacin,naproxen, codeine, oxycodone, and fentanyl citrate. In a preferredembodiment, the device is used to deliver one or more local anestheticagents. The local anesthetic agent may be a cocaine analogue. Inparticular embodiments of the device, the local anesthetic agent is anaminoamide, an aminoester, or a mixture thereof Combinations ofdifferent aminoamides or combinations of different aminoesters areenvisioned. Representative examples of possible aminoamides includelidocaine, prilocaine, mepivacaine, and ropivacaine. Representativeexamples of possible aminoesters include benzocaine, procaine,proparacaine, and tetracaine. These local anesthetics typically are weakbases and are usually formulated as a salt, such as the hydrochloridesalt, to render them water-soluble.

In a preferred embodiment, the present intravesical drug delivery deviceis used to treat inflammatory conditions such as interstitial cystitis,radiation cystitis, painful bladder syndrome, prostatitis, andurethritis. Non-limiting examples of specific drugs for these conditionsinclude lidocaine hydrochloride, glycosaminoglycans (e.g., chondroitinsulfate, sulodexide), pentosan polysulfate sodium (PPS), dimethylsulfoxide (DMSO), oxybutynin, mitomycin C, heparin, flavoxate, or acombination thereof.

The present intravesical drug delivery device can be used to treaturinary incontinence, including urge incontinence and neurogenicincontinence. Drugs that may be used include anticholinergic agents,antispasmodic agents, anti-muscarinic agents, β-2 agonists,norepinephrine uptake inhibitors, serotonin uptake inhibitors, calciumchannel blockers, potassium channel openers, and muscle relaxants.Representative examples of suitable drugs for the treatment ofincontinence include oxybutynin, S-oxybutytin, emepronium, verapamil,imipramine, flavoxate, atropine, propantheline, tolterodine, rociverine,clenbuterol, darifenacin, terodiline, trospium, hyoscyamin, propiverine,desmopressin, vamicamide, YM-46303 (Yamanouchi Co., Japan), lanperisone(Nippon Kayaku Co., Japan), inaperisone, NS-21 (Nippon Shinyaku Orion,Formenti, Japan/Italy), NC-1800 Nippon Chemiphar Co., Japan), ZD-6169(Zeneca Co., United Kingdom), and stilonium iodide.

In another embodiment, the present intravesical drug delivery device isused to treat urinary tract cancer, such as bladder cancer and prostatecancer. Drugs that may be used include antiproliferative agents,cytotoxic agents, chemotherapeutic agents, or a combination thereof.Representative examples of suitable drugs for the treatment of urinarytract cancer include Bacillus Calmette Guerin (BCG) vaccine, cisplatin,doxorubicin, methotrexate, vinblastine, thiotepa, mitomycin,fluorouracil, leuprolide, flutamide, diethylstilbestrol, estramustine,megestrol acetate, cyproterone, flutamide, and cyclophosphamide. Thedrug treatment may be coupled with a conventional radiation or surgicaltherapy targeted to the cancerous tissue.

In still another embodiment, the present intravesical drug deliverydevice is used to treat infections involving the bladder, the prostate,and the urethra. Antibiotics, antibacterial, antifungal, antiprotozoal,antiviral and other antiinfective agents can be administered fortreatment of such infections. Representative examples of suitable drugsfor the treatment of infections include mitomycin, ciprofloxacin,norfloxacin, ofloxacin, methanamine, nitrofurantoin, ampicillin,amoxicillin, nafcillin, trimethoprim, sulfa,trimethoprimsulfamethoxazole, erythromycin, doxycycline, metronidazole,tetracycline, kanamycin, penicillins, cephalosporins, andaminoglycosides.

Other drugs and excipient may be used for other therapies and at othernon-bladder body cavity sites. Combinations of two or more drugs, storedin (and released from) the same or separate reservoirs in the device areenvisioned.

The excipient of the drug formulation may be a matrix material, selectedto modulate or control the rate of release of the drug from thereservoir. In one embodiment, the matrix material may be a resorbable ornon-resorbable polymer as described above. In another embodiment, theexcipient comprises a hydrophobic or amphiphilic compound, such as alipid (e.g., selected from fatty acids and derivatives, mono-, di- andtriglycerides, phospholipids, sphingolipids, cholesterol and steroidderivatives, oils, vitamins and terpenes),

The drug formulation may provide a temporally modulated release profileor a more continuous or consistent release profile. Pulsatile releasecan be achieved from a plurality of reservoirs. For example, differentdegradable membrane can be used to by temporally stagger the releasefrom each of several reservoirs.

The Vesicle Retention Frame

As mentioned above, the drug delivery device includes a vesicleretention frame portion. The retention frame portion is associated withthe drug reservoir portion and permits retaining the drug reservoirportion in the body, such as in the bladder. The retention frame may beelastically deformed between a relatively expanded shape and arelatively lower profile shape. For example, the retention frame maynaturally assume the relatively expanded shape, may be manipulated intothe relatively lower profile shape for insertion into the body, and mayspontaneously return to the relatively expanded shape upon insertioninto the body.

The retention frame in the relatively expanded shape may be shaped forretention in a body cavity, and the retention frame in the relativelylower profile shape may be shaped for insertion into the body through alumen of a catheter. For example, the retention frame may be elasticallydeformable between a shape suited for insertion into the body throughthe working channel of cytoscope, and a shape suited for retention inthe bladder even when exposed to the forces associated with urination orcontraction of the detrusor muscle. An example of such an embodiment isshown in FIGS. 1-2, wherein the retention frame assumes a pretzel shapewhen in the expanded position, and the retention frame assumes arelatively elongated, linear shape when in the lower profile position.

To achieve such a result, the retention frame may have an elastic limit,modulus, and/or spring constant selected to impede the device fromassuming the relatively lower profile shape once implanted. Such aconfiguration may limit or prevent accidental expulsion of the devicefrom the body under expected forces. For example, the device may beretained in the bladder during urination or contraction of the detrusormuscle.

In a preferred embodiment, the retention frame includes an elastic wire.In one embodiment, the elastic wire may comprise a superelastic alloy orother shape memory material, known in the art. For example, thesuperelastic alloy may comprise a biocompatible nickel-titanium alloy(e.g., Nitinol) or a titanium-molybdenum alloy (e.g., Flexium).Biodegradable, biocompatible shape memory polymers are described in U.S.Pat. No. 6,160,084 to Langer et al. In another embodiment, the elasticwire is or includes a relatively low modulus elastomer. Low moduluselastomers may be relatively less likely to cause irritation to thebladder or to cause an ulcer once implanted. Furthermore, some lowmodulus elastomers may be completely biodegradable, which may permitcreating a device that need not be removed following implantation anddrug delivery. Examples of low modulus elastomers include polyurethane,silicone, styrenic thermoplastic elastomer, and poly(glycerol-sebacate)(PGS). The elastic wire may be coated with a biocompatible polymer, suchas a coating formed from one or more of silicone, polyurethane, styrenicthermoplastic elastomer, Silitek, Tecoflex, C-flex, and Percuflex.

For example, in the embodiment shown in FIGS. 1-2, the retention frame14 includes an elastic wire 16 formed from a superelastic alloy andcovered in a polymer coating 18. The elastic wire 16 may be, forexample, a nitinol wire. The polymer coating 18 may be, for example, asilicone sheath. In the relatively expanded or pretzel shape shown inFIG. 1, the device 10 may occupy an area having dimensions suited toimpeded expulsion from the bladder. In the relatively lower profileshape, shown in FIG. 2, the device 10 may occupy an area suited forinsertion into the body. Thus, the device 10 may fit in a catheter 20when in the relatively lower profile shape, such as the working channelof a cytoscope. Due to the properties of the elastic wire, the devicemay function as a spring. Thus, the device may deform in response to acompressive load but may spontaneously return to its initial shape oncethe load is removed. The polymer coating may make the outer surface ofthe device relatively smooth and soft, so that irritation of the bladderis avoided.

In embodiments, the retention frame may also include a radio-opaquematerial, which may improve the visibility of the device to x-ray orother imaging techniques. In the embodiment shown in FIGS. 1-2, forexample, the radio-opaque material is a platinum wire 20 wound aboutends of the elastic wire 16, although the platinum wire 20 may be woundabout other portions of the elastic wire 16. A smoothening material mayalso be applied to ends of the elastic wire to reduce the bluntness ofthe ends. In the embodiment shown in FIGS. 1-2, for example, thesmoothening material 22 is an ultraviolet-curable epoxy applied to theends. The ultra-violet epoxy may also assist with retaining the platinumwire 20 in place.

In embodiments in which the retention frame assumes a pretzel shape, theretention frame may be relatively resistant to compressive forces. Apretzel shape essentially comprises two sub-circles, each sub-circlehaving its own smaller arch and the sub-circles sharing a common largerarch. When the two sub-circles are first compressed together, thelargest arch absorbs the majority of the compressive force and beginsdeforming. With continued application of the compressive force, thesmaller arches of the two sub-circles overlap. Subsequently, all threeof the arches resist the compressive force. The resistance tocompression of the device as a whole increases once the two sub-circlesoverlap. Such a configuration may prevent collapse of the device as thebladder contracts during urination, to impede accidental voiding fromthe bladder. Example 4 explains this result in greater detail.

In embodiments in which the retention frame comprises a shape memorymaterial, the material used to form the frame may “memorize” therelatively expanded shape and may spontaneously assume the relativelyexpanded shape upon the application of heat to the device. For example,the retention frame may be designed to return to the relatively expandedshape when exposed to body temperatures, so that the device may expandupon entering the bladder.

The retention frame may be in a form having a high enough springconstant to retain the device within a body cavity, such as the bladder.This may be accomplished by forming the retention frame from a highmodulus material or a low modulus material. Particularly, in embodimentsin which the retention frame is formed from a relatively low modulusmaterial, the retention frame may be formed into a configuration havinga diameter and/or a shape that provides an appropriate spring constant.In one case, the elastic wire may comprise a low modulus elastomer in aform having a spring constant without which the elastic wire wouldotherwise experience significant deformation when subjected to theforces associated with urination. For example, the elastic wire of theretention frame may include one or more windings, coils, spirals, orcombinations thereof, which may reduce the tendency of the elastic wireto deform during urination. In other words, the elastic wire may act asa spring due to the windings, coils, and/or spirals, even in cases inwhich the elastic wire is formed from a low modulus elastomer, such aspolyurethane or silicone.

The windings, coils, or spirals may be specifically designed to achievea desirable spring constant. In various embodiments, the spring constantmay be in the range of about 3 N/m to about 60 N/m. For example, thespring constant may be in the range of about 3.6 N/m to about 3.8 N/m.Such a spring constant may be achieved by one or more of the followingtechniques: increasing the diameter of the elastic wire used to form theframe, increasing the curvature of one or more windings of the elasticwire, and adding additional windings to the elastic wire. Example springconstants for certain low modulus wires are provided in Example 5,below.

The windings, coils, or spirals of the frame may have a number ofconfigurations. For example, the frame may be in a curled configuration,such as in a configuration comprising one or more loops, curls orsub-circles. FIG. 6 illustrates example shapes for the frame thatinclude one or more loops, curls, or sub-circles. The curls may beintegrally connected in a linear fashion, as shown in Examples B, C, D,and E, or in a radial fashion, as shown in Examples F and G. The curlsmay turn in the same direction, as shown in Examples B and E, or inalternating directions as shown in Examples C and D. The curls may alsooverlap, as shown in Examples A, B, and E. The opposing ends of theelastic wire may be adapted to avoid tissue irritation and scarring. Forexample, the ends may be soft, blunt, inwardly directed, joinedtogether, or a combination thereof The frame may also include a one ormore circles or ovals arranged in a two-dimensional or athree-dimensional configuration. FIG. 7 illustrates example shapes forthe frame that include one or more circles or ovals arranged in atwo-dimensional or a three-dimensional configuration. The frame mayinclude a number of concentric circles, as shown in Example A, or anumber of concentric ovals, as shown in Examples B and C. Each of thecircles or ovals may be closed, and the circles or ovals may be joinedat a common connecting point. Alternatively, one or more of the circlesand ovals may be open. The circles and ovals may also be connected at anumber of connecting points. The frame may also include a number ofoverlapping circles or ovals. The overlapping circles or ovals may eachbe substantially the same size, as shown in Example D, or the circles orovals may vary in size, as shown in Examples E and F. Circles may alsobe combined with ovals, depending on the embodiment. Further, the framemay be an open-ended spiral, as shown in Example G, or the frame may bea spiral having closed ends.

Combination of the Components

The vesicle retention frame is associated with the drug reservoirportion to form the drug delivery device. A variety of differentassociations are envisioned. For example, the drug reservoir portion maybe attached to an intermediate region of the vesicle retention frame.More specifically, the vesicle retention frame may have a first end, anopposing second end, and an intermediate region therebetween, and thedrug reservoir portion may have first and second end portions that areattached to the intermediate region of the vesicle retention frame. Theend portions of the drug reservoir may terminate at the vesicleretention frame, the end portions may overlap the vesicle retentionframe, or a combination thereof. The drug reservoir portion may beoriented with reference to the retention frame such that the drugreservoir portion lies within the perimeter of the retention frame,beyond the perimeter of the retention frame, or a combination thereof.Additionally, a number of drug reservoir portions may be associated asingle retention frame, depending on the configuration of the device.

FIG. 8 illustrates example embodiments of a pretzel shaped retentionframe 80 having one or more drug reservoirs 82 attached at anintermediate region of the retention frame 80. Specifically, Example Aillustrates an embodiment having one drug reservoir, wherein the drugreservoir lies within the perimeter of the retention frame and has endportions attached to the intermediate region of the retention frameterminating at the retention frame. Example B illustrates an embodimenthaving one drug reservoir, wherein the drug reservoir lies outside ofthe perimeter of the retention frame and has end portions attached tothe intermediate region of the retention frame slightly overlapping theretention frame. Example C illustrates an embodiment having a number ofdrug reservoir portions, each drug reservoir portion lying within theperimeter of the retention frame, and Example D illustrates anembodiment having a number of drug reservoir portions, some of the drugreservoir portions lying within the perimeter of the retention frame andsome of the drug reservoir portions lying outside of the of theperimeter of the retention frame.

In one embodiment, multiple drug reservoir portions are associated witha single retention frame. For example, FIG. 9 shows an embodiment of aretention frame 90 having a number of drug reservoir portions 92attached at an intermediate region of the retention frame 90, with thedevice shown in a relatively expanded shape in FIG. 9A and the deviceshown in a relatively lower profile shape within a catheter in FIG. 9B.Including multiple discrete drug reservoir portions may facilitatedelivering multiple different drugs into the body, delivery differentforms of drugs into the body, delivery drugs at varying rates into thebody, or a combination thereof.

In other embodiments, the drug reservoir portion and the vesicleretention frame portion may be at least partially aligned. In otherwords, the drug reservoir portion may extend along at least a portion ofthe length of the retention frame portion, substantially parallel orcoincident with the retention frame portion. For example, the drugreservoir portion may extend along the entire length of the retentionframe portion. Examples of such embodiments are shown in FIG. 10, whichillustrates several alternative embodiments in cross-section. Althoughonly one cross-section is shown, the device may have the samecross-section, or a similar cross-sectional configuration, alongsubstantially the entire length of the device or along a substantialportion of the device. The retention frame may comprise an elastic wire102 associated with the tube 100 of the drug reservoir portion, as shownin Examples A, B, C, and D. The elastic wire 102 may extend along anexterior surface of the tube 100 as shown in Example A. The elastic wire102 also may extend along an interior surface of the tube 100, as shownin Example C. The elastic wire 102 may also extend through the surfaceof the tube 100, as shown in Example B. In embodiments, the tube 100 maybe strengthened near the elastic wire 102 with a reinforcement area 104,which may reduce the risk of the elastic wire 102 tearing through orbecoming detached from the tube 100. For example, the reinforcement area104 may be an area of additional silicone. The elastic wire 102 may alsobe positioned within the interior of the tube 100 supported by a web106, as shown in Examples E, F, and G. In addition to supporting theelastic wire 102, the web 106 may partition the tube 100 into multiplecompartments. For example, the web 106 partitions the tube 100 into twocompartments in Example E, three compartments in Example F, and fourcompartments in Example G, although other configurations are possible.The web 106 may be perforated or otherwise non-continuous so that thecompartments are in communication with each other. Alternatively, theweb 106 may be relatively continuous such that the compartments aresegregated from each other. In such embodiments, the discretecompartments may form different reservoirs that may be suited forholding different drug formulations. The web 106 may be formed from thesame material as the tube, or from a material having a differentpermeability to water or urine, depending on the embodiment.

In still other embodiments, the elastic wire may be associated withmultiple tubes, extending along or between the tubes. Examples of suchembodiments are shown in FIG. 11, which illustrates several alternativeembodiments in cross-section. In such embodiments, multiple discretetubes 110 may be joined together by a reinforcement area 114, with theelastic wire 112 embedded in the reinforcement area 114, as shown inExamples A, B, and C. The number of tubes 110 may vary. For example, twotubes 110 are shown in Example A, three tubes 110 are shown in ExampleB, and four tubes 110 are shown in Example C, although additional tubesmay be provided in embodiments not shown. In such embodiments, the sameor different drug formulations may be loaded in the discrete tubes 110.The discrete tubes 110 may also be formed from the same or differentmaterials of construction, such as materials that differ in permeabilityto urine or other aqueous or bodily fluids.

The embodiments described above may be combined and varied to produceother drug delivery devices that fall within the scope of the presentdisclosure. For example, the drug reservoir portion may be attached toany portion of the retention frame in any manner, than the intermediateregion. Also, the drug reservoir portion may be wrapped around theelastic wire of the retention frame, one or any number of times. Itshould be noted that the retention frame is generally described as beingan elastic wire for the sake of simplicity, and that the elastic wiremay be coated with a polymer tubing in any of these embodiments, asdescribed above with reference to FIG. 1. Also, the term “drug reservoirportion” generally refers to the discrete tube that is associated withthe retention frame, although this tube may be separated or otherwisepartitioned into any number of discrete drug reservoirs, as describedabove with reference to FIG. 4 and FIG. 11. Providing multiple drugreservoir portions, partitioning a single drug reservoir portion intomultiple drug reservoirs, or a combination thereof, may facilitatedelivering multiple different drugs into the body, delivery differentforms of drugs into the body, delivery drugs at varying rates into thebody, or a combination thereof. For example, the device may hold a drugin both a liquid form for earlier release upon implantation and in solidor semi-solid form for later release after the drug is solubilized.

The drug reservoir component can be attached to the vesicle retentionframe using essentially any biocompatible material or structure. Forexample, the drug reservoir portion may be attached to the retentionframe using a medical grade silicone adhesive.

In embodiments, the drug reservoir component may be attached to thevesicle retention frame by at least partially imbedding the elastic wireof the retention frame within the elastomeric tube of the drug reservoirportion. In the embodiment illustrated in FIG. 12, a portion of apretzel shaped elastic wire 120 extends through first and second ends ofa drug reservoir portion 122, although other configurations arepossible. In such embodiments, the tubing of the drug reservoir portionmay be formed with the wire in it, or the tube may be penetrated by thewire after both parts are formed, to connect them.

In still other embodiments, the drug reservoir portion may be integrallyformed with the retention frame. For example, a casting method may beused, which may include pouring a curable silicone into a mold andallowing the silicone to cure. In some such embodiments, the elasticwire may be positioned in the mold along with the silicone.

Further, the drug reservoir portion and the retention frame portion maybe the same component in some embodiments. In such cases, the device maycomprise a silicone tubing formed in a configuration having a sufficientspring constant to retain the device in the body, as described above. Insuch cases, attachment may not be necessary.

Other Device Features

The rate and total amount of drug delivered from a single device maydepend on, for example, the surface area of the drug reservoir portion,the type and permeability of the materials of construction of the drugreservoir portion, the number of apertures formed through the drugreservoir portion, and the total mass of drug load, among others.Particular target therapeutic dosages and acceptable implant dimensionsfor a particular body cavity and route of implantation can be selectedfor different drugs and therapies.

In embodiments, the drug reservoir portion can be partially or whollycoated with a coating or a sheath, which may facilitate controlling therelease rate. The coating or sheath may be relatively less permeable towater than the drug reservoir portion. Thus, the coating or sheath maymodulate or reduce the water permeability of the drug reservoir portionto control or slow the rate of release of the drug from the device. Insome cases, the coating or sheath may be partially permeable to water,in which case the coating or sheath may cover all or a portion of thedrug reservoir portion. For example, the coating or sheath may comprisea mesh that covers substantially the entire device. In other cases, thecoating or sheath may be substantially impermeable to water, in whichcase the coating or sheath may cover only a portion of the device body.Regardless, the coating or sheath may reduce or alter the osmoticsurface area of the device body. Due to the reduced or altered osmoticsurface area, the release rate of drug from the drug reservoir portionmay be reduced or altered.

Because the coating or sheath may permit controlling the release rate,the drug reservoir portion may be sized, shaped, and constructed tohouse a certain drug payload volume, to achieve a certain flexibility orspring constant or to assume a certain shape during implantation or onceimplanted, among others. These characteristics of the drug reservoirportion may be selected without regard to how such characteristicsaffect the release rate, as the release rate may be independentlycontrolled by controlling the osmotic surface area with the coating orsheath. Thus, the release rate may be altered without changing theoverall size of the device body, the shape of the device body, or thematerials used to form the device body.

In cases in which the drug reservoir portion is formed from siliconetubing, the coating or sheath may be formed from a material that isrelatively less permeable to water or urine than silicone. For example,the coating or sheath may be formed from a polymer, parylene, a curablesilicone, or another biocompatible coating or sheath material known inthe art. In one embodiment, the device body may be formed from silicontubing, while the sheath may be formed from polyurethane.

The coating or sheath may have be relatively uniform along the devicebody to facilitate relatively uniform release of the drug from thereservoir. Alternatively, the coating or sheath may vary along thedevice body, so that certain parts of the device body have higher orlower water permeability relative to other parts of the device body. Forexample, one or more characteristics of the coating or sheath may varyover the device body to achieve the desired release rate. Examplecharacteristics of the coating or sheath that may vary includethickness, size, or shape of the coating or sheath; position, location,or orientation of the coating or sheath on the device body; and materialused to form the coating or sheath, among others.

Further, multiple coatings or sheaths may be provided along differentportions of the device body. In some cases, the multiple coatings orsheaths may correspond to multiple reservoirs formed in the device body,each of the multiple reservoirs containing a different drug. In suchcases, the multiple coatings or sheaths may have the samecharacteristics to permit relatively uniform release of the differentdrugs from the different reservoirs. Alternatively, the multiplecoatings or sheaths may have differing characteristics to permitdiffering release rates of the different drugs from the differentreservoirs. Example coating or sheath characteristics that may differ tovary the release rate include thickness, size, shape, position, andmaterial, among others, as described above. For example, the tube arounda first reservoir may be coated with a first coating of a first materialand a first thickness, while the tube around a second reservoir may beuncoated, coated with a second (different) coating material, or coatedwith the first coating material but at a second (different) thickness.Thus, the release rate from the first reservoir may differ from therelease rate from the second reservoir.

In embodiments, the positioning of the coating or sheath about thedevice body may be selected to augment or otherwise control dissolutionof solid or semi-solid forms of the drug. An example is shown in FIG.13. As shown, the device body 130 may be formed from a tube 132, such asa silicone tube. The tube 132 may have two opposed ends 133. Amicrosphere 134 may enclose each of the ends 133, and a reservoir 135may be formed between the ends 133. An orifice 136 formed through thetube 132 may permit releasing a drug from the reservoir 135. To controlthe release of the drug from the orifice 136, at least one sheath 138may be positioned about the tube 132. For example, a sheath 138 may bepositioned on each side of the tube 132 between the orifice 136 and theend 133. So that the drug does not become stagnated below the sheath138, the sheath 138 may be spaced inward from the end 133. As shown, thesheath 138 may be relatively closer to the orifice 136 than to the end133, such as directly adjacent to the orifice 136, although otherconfigurations are possible. Such placement of the sheath 138 mayfacilitate releasing the drug from the orifice 136, as the positioningmay permit water to permeate the tube 132 adjacent to the end 133. Aswater permeates through the tube 132 adjacent to the end 133, the drugmay be driven through the portion of the tube 132 covered by the sheath138 and out of the orifice 136. Thus, isolation or stagnation of thedrug positioned under the sheath 138 may be avoided. Examples 11 and 12,below, provide release rate data for a drug delivery device having asheath, and also provide example equations for selecting the length ofsheath to achieve a desired release rate.

In a preferred embodiment, the tube preferably includes at least oneradio-opaque portion or structure to facilitate detection or viewing ofthe device as part of the implantation or explantation procedure. In oneembodiment, the tube is constructed of a material that includes aradio-opaque filler material, such as barium sulfate or anotherradio-opaque material known in the art.

Silicone tubing may be made radio-opaque (for X-ray imaging orfluoroscopy) by blending radio-opaque fillers, such as barium sulfate orother suitable materials, during the processing of the tubing.Ultrasound imaging can also detect silicone in vivo, but it may sufferfrom lack of resolution to be able to correctly image the device if thelatter is kept small. Fluoroscopy may be the preferred method duringdeployment/retrieval of the non-resorbable device by providing accuratereal-time imaging of the position and orientation of the device to thepractitioner performing the procedure.

In one embodiment, the body of the intravesical drug delivery devicefurther includes at least one retrieval feature. The retrieval featuremay be a structure that facilitates removal of the device from the bodycavity, for example for removal of a non-resorbable device bodyfollowing release of the drug formulation. Embodiments of retrievalfeatures are described in U.S. patent application Ser. No. 11/463,956,which is incorporated by reference above. In these and in otherembodiments, the device may be retrieved using conventional endoscopicgrasping instruments, such as alligator forceps, three or four-prongedoptical graspers. For example, if the device has an O-shaped or coiledportion, the removal of the device can be facilitated by those graspinginstruments.

In embodiments, the device may be designed to administer drugs toachieve an immediate affect during an acute phase and to achieve aprolonged effect during a maintenance phase. For example, the device mayhave two drug reservoirs or drug reservoir portions, one of which isconfigured to release a drug relatively quickly after implantation andone of which experiences an induction time before beginning release. Toaccomplish such a result, the two drug reservoirs or drug reservoirportions may have different configurations, such as differentpermeabilities, or the two drug reservoirs or drug reservoir portionsmay store different forms of the drug, such as a liquid form forimmediate release and a solid form to be solubilized prior to release.These embodiments can be combined and varied with other embodimentsdescribed herein to achieve the desired release profile.

II. Method of Making the Device

In another aspect, a method of making an implantable drug deliverydevice is provided. FIG. 14 is a block diagram illustrating anembodiment of such a method 140. In block 142, a drug reservoir portionis formed. In block 144, a vesicle retention frame portion is formed. inblock 146, the drug reservoir portion is associated with the vesicleretention frame portion.

In embodiments, forming the drug reservoir portion in block 142 mayinclude one or more of the following sub-steps: forming the drugreservoir tube, forming a relatively solid drug rod, loading the drugrod into the tube, inserting a sealing material into the tube between anend of the drug rod and an end of the tube, and forming one or moreapertures in the tube.

The drug reservoir tube may be formed using conventional methods, suchas injection molding, compression molding, extrusion molding, transfermolding, insert molding, thermoforming, casting, or a combinationthereof The hollow tube may be formed from a material that isbiocompatible, water permeable, elastic, or any combination thereof. Forexample, the tube may comprise silicone.

The drug rod may be formed by filling a mold with an aqueous solutioncomprising the drug and allowing a solvent to evaporate from thesolution. For example, a lidocaine drug rod may be formed by filling amold with an aqueous solution of lidocaine, allowing at least a portionof the solvent to evaporate to form a saturated or super saturatedsolution of the drug, and then crystallizing the resulting gel to form alidocaine drug rod. A seed crystal may be introduced into the saturatedor supersaturated solution to initiate crystal growth and thusprecipitation of the drug. In such cases, the evaporation andcrystallization steps may be done at one or more controlledtemperatures. As another example, lidocaine hydrochloride may becombined, e.g., in a 70:30 mixing ratio, with chondroitin sulfate C, toproduce a drug rod with some stiffness to enhance handling of thedevice, although such a process sacrifices some of the payload oflidocaine hydrochloride. Whether that sacrifice is acceptable depends onthe particular device design and application/use

In embodiments in which a drug rod is formed, the tube of the drugreservoir portion may or may not serve as the mold. In embodiments inwhich the tube does not serve as the mold, the completed drug rod may beloaded into the tube by manipulating the drug rod into the tube using,for example, a guide wire and/or tweezers.

In embodiments in which the drug formulation is in liquid form, the drugformulation may be loaded into the drug reservoir portion through theapertures or through another opening that it subsequently sealed.However, it may be relatively easier to load the drug in solid orsemi-solid form, and such forms may further reduce the size of thedevice, which may facilitate reducing irritation to surrounding tissue.

The one or more apertures may be formed in one or more of the following:the side wall of the tube, an end of the tube, or a combination thereof.The one or more apertures may be formed by laser drilling one or moreholes in the tube. The laser drilling may occur before or after the drugrod is loading into the tube. Alternatively, the apertures may be formedsimultaneously with the device body, such as by molding with an indenteras described in U.S. Pat. No. 6,808,522 to Richards et al.

In embodiments, forming the drug reservoir portion in block 142 maycomprise forming multiple different drug reservoirs in a single drugreservoir portion. In such embodiments, one or more partitioningstructures may be inserted into and positioned within the tube, forexample using a guide wire. In cases in which multiple reservoirs andpartitions are used, the installation of the partition structures may bealternated with the loading of the drug formulation. The position of thepartition structure may be secured using adhesive or by frictionalengagement with the tube, such as in cases in which the partition has aslightly larger outer diameter than the inner diameter of the tube.

In embodiments, forming the drug reservoir portion in block 142 mayfurther include associating one or more release controlling structureswith the drug reservoir portion. For example, a sheath or coating may beplaced over at least a portion of the surface of the tube to control therate of release of the drug. Additionally, a degradable membrane may bepositioned over or in one or more of the apertures to control theinitial time of release of the drug therethrough. The degradablemembranes may be formed by microinjecting or inkjet printing a fluid toform a membrane at one end of the aperture, e.g., in/on the outersurface opening in the tube. For example, the fluid may be a solutioncomprising a resorbable material dissolved in a solvent, a suspensioncomprising a resorbable material in a nonsolvent, or a liquefiedresorbable material. Also, the drug reservoir portion may be formed froma drug polymer composite designed to release at a known rate.

In embodiments, the step of forming a vesicle retention frame portionmay vary depending on the material used to form the frame. Inembodiments in which the retention frame comprises an elastic wireformed from a superelastic alloy or shape memory material, for example,the step of forming the vesicle retention frame may comprise forming theelastic wire into the relatively expanded shape and “programming” theshape into the elastic wire via heat treatment. For example, theretention frame 14 shown in FIG. 1 may be formed by forming the elasticwire 16 into a pretzel shape and heat treating the elastic wire 16 at atemperature over 500° C. for a period over five minutes. Also in suchembodiments, forming the vesicle retention frame portion may include oneor more of the following: forming a polymer coating or sheath over theelastic wire, smoothening the ends of the elastic wire, and applying aradio-opaque material to at least a portion of the elastic wire. In suchembodiments the polymer sheath, the radio-opaque material, and thesmoothening material may be applied to the elastic wire in any order.For example, a platinum wire may be wound around ends of the elasticwire to improve the radio-opacity of the device to x-ray, the ends ofthe elastic wire may be smoothened with an ultraviolet-curable epoxy,and the polymer sheath or coating may be placed over the elastic wire.

In embodiments in which the retention frame comprises a low moduluselastomer, the step of forming the vesicle retention frame maycomprising forming one or more windings, coils, loops or spirals in theframe so that the frame functions as a spring. For example, theretention frame may be formed by extrusion, liquid injection molding,transfer molding, or insert molding, among others.

In embodiments, the step of associating the drug reservoir portion witha vesicle retention frame portion may comprise orienting the drugreservoir portion with reference to the retention frame portion andapplying an adhesive therebetween. The drug reservoir portion may beoriented in a variety of orientations as described above. In otherembodiments, the step of associating the drug reservoir portion with thevesicle retention frame portion may comprise inserting an elastic wireof the retention frame portion at least partially through the drugreservoir portion. In still other embodiments, the step of associatingthe drug reservoir portion with the vesicle retention frame portion maycomprise integrally forming the two portions together.

III. Use and Applications of the Device

The intravesical drug delivery device may be used to deliver druglocally to essentially any body cavity site. In a preferred embodiment,the body cavity may be the bladder of a male or female human patient inneed of treatment. For example, the intravesical drug delivery devicemay be used in the treatment of interstitial cystitis, radiationcystitis, overactive bladder syndrome, or bladder cancer, although thedevice also may deliver drug to the bladder for the treatment of otherconditions. In other embodiments, the present intravesical devices maybe used in other body cavities of a patient. For example, the smalldevices may be implanted in a space in the vagina, a gastric cavity, theperitoneal cavity, or an ocular cavity.

In one embodiment, the intravesical drug delivery device is implantedinto a patient's bladder to locally deliver a local anesthetic agent formanagement of pain associate arising from any source. For example, itmay be pain from any disease or disorder in genitourinary tissues, painstemming from any bladder catheterization procedure itself e.g.,post-operative catheterization.

The device may be implanted in the bladder of a patient by any suitablelumen device, generally referred to herein as a catheter, urethralcatheter, or cystoscope, as known in the art. These terms are usedinterchangeably herein, unless otherwise expressly indicated. Thecatheter may be a commercially available device or one specially adaptedto accommodate an embodiment of the present drug delivery devices.

In one example, a method of implanting an intravesical drug deliverydevice in a body cavity comprises passing the intravesical drug deliverydevice through a catheter in a relatively low-profile shape, andreleasing the device from the catheter into the body cavity, the deviceassuming a relatively expanded shape once the device emerges from thecatheter for retention in the body cavity. In embodiments, therelatively lower profile shape may be a relatively linear, folded,expanded, or compressed form. The catheter may be inserted into theurethra to permit access to the bladder. FIG. 15 illustrates anembodiment of the releasing step of the method. As shown in FIG. 15, thedevice 152 may be pushed through a catheter 150 using a stylet 154. Asshown, the device 152 changes shape as it emerges from the catheter 150,returning to the relatively expanded shape for retention in the bladder.U.S. Pat. No. 6,139,535 also describes a method and apparatus forplacement of a medical device in the bladder through the urethra.

In embodiments, the intravesical drug delivery device comprises a drugin a relatively solid form, such as a drug rod or a powder form. Elutionof drug from the device occurs upon dissolution of the drug rod. Thatis, as the drug contacts and becomes solubilized in bodily fluid thatenters the device, the dissolved drug diffuses or flows under osmoticpressure from the implanted device. For example, the device may bedelivered into the bladder, in which case the drug may be solubilizedupon contact with urine in the bladder.

In one embodiment, the intravesical drug delivery device isnon-resorbable or otherwise needs to be removed following implantation.In one such a case, the method described in the preceding paragraphfurther includes removing the intravesical drug delivery device from thebody cavity following release of the drug. Specialized retrieval devicesare known in the art, or can readily be produced, for this purpose. Forexample, U.S. Pat. No. 5,499,997 describes an endoscopic grasping methodand apparatus.

The device may be used to deliver drugs locally to the bladder as analternative to systemic delivery, which may be desirable in cases inwhich systemic delivery may cause undesirable side effects or result ininsufficient bioavailability of the drug.

The present intravesical drug delivery device treatment method providesextended, continuous, intermittent, or periodic release of a desiredquantity of drug over a desired (predetermined) period of time. In oneembodiment, the device can deliver the desired dose of drug over anextended period of time, e.g., 24 hours, 5 days, 7 days, 10 days, 14days, or 20, 25, 30, 45, 60, or 90 days, or more. The rate of deliveryand dosage of the drug can be selected depending upon the drug beingdelivered and the disease/condition being treated. The use of differentdegradation rates and/or excipient materials, along with varying thenumber and size of apertures in the device, can be used to tailor thedevice to have different release kinetics.

In a preferred embodiment, the device is administered to (i.e.,implanted into) the bladder of a patient and delivers in a controlledmanner a drug formulation to the bladder. In particular embodiments, thedrug formulation includes one or more drugs useful in the treatment ofoveractive bladder syndrome, bladder cancer, interstitial cystitis, orpain relief.

For example, the device may be used to deliver lidocaine locally to thebladder over an extended time period, such as a period of more than oneday. Advantageously, the device enables the delivery, of lidocaine forexample, to the bladder to provide an increase in the localconcentration of lidocaine in the bladder tissue without producing highsystemic levels.

FIG. 16 is a block diagram illustrating a method 160 of deliveringlidocaine to the bladder. In block 162, a device having a payload oflidocaine is delivered to the bladder. In block 164, the lidocaine iscontinuously released from the device over an extended period of time.In such embodiments, the device may be an embodiment of the devicedescribed above, or the device may be any other device. In embodiments,the payload of lidocaine may be in the range of about 50 mg to about 100mg. The extended period of time may be in the range of about one day toabout fourteen days, for example. Such a method may achieve a sustainedlevel of lidocaine in the urothelium of the bladder.

Advantageously, the sustained level of lidocaine in the urotheliumachievable with the present devices and methods can exceed the levelthat is generally considered to be tolerable systemically. High localconcentrations of drug are provided without significant systemicconcentrations. This enables the effective use of a relatively smallpayload of lidocaine to create a therapeutically effective concentrationof lidocaine in the urothelium. The urothelium lidocaine concentrationmay exceed the concentration that could be obtained systemically withoutcausing systemic effects. The urothelium lidocaine concentration mayalso exceed the concentration that could be obtained via instillation,and further, the high initial peak concentration associated withinstillation may be avoided. The small payload may facilitate devicesafety, as the payload may be sufficiently small to avoid undesirablesystemic effects even in the event of device failure. Yet, the smallpayload may create an effective concentration of lidocaine in theurothelium, due to the local nature of the delivery. See Example 8below.

In embodiments, the method may delivery the lidocaine without regard tothe pH of the urine. For example, the lidocaine need not be administeredwith a buffering agent, such as sodium bicarbonate. See Example 9 below.

In embodiments, the method may deliver the lidocaine in relatively solidform, which may permit reducing the size of the device to avoid bladderirritation and patient discomfort.

In embodiments, (1) delivering a device having a payload of lidocaine tothe bladder may comprise delivering a device to the bladder that hasfirst and second payloads of lidocaine; and (2) continuously releasingthe lidocaine from the device over an extended period of time maycomprise initiating release of the first payload of lidocaine andsubsequently initiating release of the second payload of lidocaine. Thefirst payload may be adapted for relatively quick release, while thesecond payload may be adapted for more continuous release. For example,the first payload may be in liquid form while the second payload may bein solid form. As another example, the first payload may be housed in arelatively fast-acting osmotic pump, such as a silicone tube having arelatively thinner wall, while the second payload may be housed in anosmotic pump that experiences an initial delay or induction time beforereleasing, such as a silicone tube having a relatively thicker wall.Thus, the method may continuously release lidocaine into the bladderduring an initial, acute phase and during a maintenance phase. Such amethod may compensate for an initial induction time of the device, asdescribed below with reference to Example 8.

The present invention may be further understood with reference to thefollowing non-limiting examples.

EXAMPLE 1 Design of a Tubular Osmotic Pump

Described below is the design of a tubular osmotic pump made ofsilicone. Other biocompatible polymer tubes such as polyurethane can beused depending on the permeability to water (and drug) and mechanicalproperties. Design equations for the tubular osmotic pump permitobtaining the desired drug payload and release rate. Tube thickness isrelated to mechanical integrity and water permeability. Tube innerdiameter and tube wall thickness determine the drug payload and outerdiameter of the tube. Tube length affects both drug payload as well asthe macro size or loop diameter of the tubular osmotic pump. Osmoticsurface area over which water or urine can permeate through the tube isaffected by tube outer diameter and tube length. These parametersinfluence the overall performance of the osmotic pump.

The tubular osmotic pump holds a drug on an interior reservoir, and iscapable of transfer the drug to an outside medium Parameters of thetubular osmotic pump are defined below.

C: instantaneous drug concentration in the device reservoir

ρ: drug density

S: drug solubility

d: tube inner diameter

h: tube wall thickness

D: diameter of macro loop made of tube

L: tube total length, L=πD

L_(n); tube length without permeation blocking sheath

L_(s): tube length with permeation blocking sheath, L_(s)=L−L_(n)

V: volume of drug reservoir,

$V = \frac{\pi \; d^{2}L}{4}$

m: instantaneous drug amount remaining in the device reservoir,

$m = {{CV} = {C\frac{\pi \; d^{2}}{4}L}}$

m_(p): total drug payload,

$m_{p} = {{\rho \; V} = {\rho \frac{\pi \; d^{2}}{4}L}}$

ΔΠ: osmotic pressure difference between the inside and outside of thetube

ΔΠ_(s): osmotic pressure difference at saturation between the inside andoutside of the tube

k: permeability coefficient for solvent transport

Λ: osmotic surface area for water permeation, A=π(d+h)L_(n)

t_(z): duration of zero order release

$\frac{dm}{dt}\text{:}$

the rate of drug mass change in the reservoir,

$\frac{dm}{dt} = {{- {kA}}\frac{\Delta\Pi}{h}C}$

{dot over (m)}_(z): zero order release rate,

${\overset{.}{m}}_{z} = {\left. {- \frac{dm}{dt}} \right|_{zero} = {{kA}\frac{{\Delta\Pi}_{S}}{h}S}}$

m_(z): amount released during zero order release, m_(z)={dot over(m)}_(z)·t_(z)

The parameter ‘dm/dt’ is defined as the rate of drug mass loss in thedevice reservoir since ‘m’ indicates the instantaneous drug amountremaining in the device reservoir. The minus sign in the expression‘dm/dt’ reflects the fact that the device will lose its drug by osmoticrelease once the device is immersed in water or urine. When the osmoticpressure of the surrounding medium is small enough compared to theosmotic pressure of the formulation inside the drug reservoir, van'tHoff's law can be used to obtain:

$\begin{matrix}{\frac{\Delta \prod_{C}}{\Delta \; \prod_{S}} = \frac{C}{S}} & (1.1)\end{matrix}$

where the proportional relationship between the osmotic pressure andconcentration is used.

The drug release rate from the device remains constant at the initialtime period when the concentration inside the drug reservoir is thesolubility of drug loaded. The amount of drug released during thisinitial ‘zero-order release period’ can be expressed as

$\begin{matrix}{m_{z} = {\left( {1 - \frac{S}{\rho}} \right)m_{p}}} & (1.2)\end{matrix}$

The drug release rate decreases after the zero-order release period asthe drug concentration inside the reservoir becomes reduced. The rate ofdrug mass change (dm/dt) in the reservoir can still be expressed interms of zero order release rate ({dot over (m)}_(z)):

$\begin{matrix}\begin{matrix}{\frac{m}{t} = {{- {kA}}\; \frac{\Delta\prod}{h}C}} \\{= {\left( {{- {kA}}\; \frac{\Delta \prod_{S}}{h}S} \right)\frac{C}{S}\frac{\Delta\prod}{\Delta \prod_{S}}}} \\{= {{- {\overset{.}{m}}_{z}}\frac{C^{2}}{S^{2}}}}\end{matrix} & (1.3)\end{matrix}$

The expressions for the amount of drug remaining in the reservoir (m)and the rate of drug mass change (dm/dt) are different for two timeperiods, the zero order release period and the non-zero order releaseperiod. The expressions for the zero-order release period (0≦t≦t_(z))are:

$\begin{matrix}{m = {m_{p} - {{\overset{.}{m}}_{z}t}}} & (1.4) \\{\frac{m}{t} = {- {\overset{.}{m}}_{z}}} & (1.5)\end{matrix}$

Eq. (1.3) may be integrated to find the expressions for the non-zeroorder release period (t≧t_(z)). Drug concentration (C) and drug mass (m)are time-dependent variables and are related by

m=CV   (1.6)

After combining Eq. (1.6) with Eq. (1.3), Eq. (1.3) may be integratedfrom t_(z) to t to obtain

$\begin{matrix}{{\int_{SV}^{m}{m^{- 2}{m}}} = {\int_{z}^{t}{{- \frac{{\overset{.}{m}}_{z}}{({SV})^{2}}}{t}}}} & (1.7)\end{matrix}$

Drug mass remaining inside the reservoir at time t (≧t_(z)) can beexpressed as

$\begin{matrix}{{m = {\frac{S}{\rho}{m_{p}\left\lbrack {1 + {\frac{\rho}{S}\frac{{\overset{.}{m}}_{z}}{m_{p}}\left( {t - t_{z}} \right)}} \right\rbrack}^{- 1}}}{and}} & (1.8) \\{{\frac{m}{t} = {- {{\overset{.}{m}}_{z}\left\lbrack {1 + {\frac{\rho}{S}\frac{{\overset{.}{m}}_{z}}{m_{p}}\left( {t - t_{z}} \right)}} \right\rbrack}^{- 2}}}{where}} & (1.9) \\{t_{z} = {\left( {1 - \frac{S}{\rho}} \right)\frac{m_{p}}{{\overset{.}{m}}_{z}}}} & (1.10)\end{matrix}$

The drug mass in the device reservoir beyond t_(z) can be expressed as

m=αm _(p)α≦1)   (1.11)

where α is the ratio parameter indicating remaining drug mass comparedto the initial loading (for example, if α is 0.05, then 5% of the totalpayload remains in the device or 95% of the total loading is releasedout). Substituting Eq. (1.11) into Eq. (1.8) gives the time t as

$\begin{matrix}{t = {{t_{z} + {\frac{m_{p}}{{\overset{.}{m}}_{z}}\left( {{- \frac{S}{\rho}} + {\frac{1}{\alpha}\frac{S^{2}}{\rho^{2}}}} \right)}} = {\frac{m_{p}}{{\overset{.}{m}}_{z}}\left( {1 - {2\; \frac{S}{\rho}} + {\frac{1}{\alpha}\frac{S^{2}}{\rho^{2}}}} \right)}}} & (1.12)\end{matrix}$

where t_(z) is replaced by Eq. (1.10). Eq. (1.12) reveals that

$\frac{m_{p}}{{\overset{.}{m}}_{z}}$

is the factor determining the delivery time scale. This result impliesthat total payload and initial zero order release rate decides theoverall behavior of drug release profile over time.

EXAMPLE 2 Comparison of Release Profiles for Differing Devices

Examples of the application of Eq. (1.12) are presented here. FIG. 17illustrates three different devices A, B, and C, and FIG. 18 is a graphillustrating in vitro drug release profiles for the three differentdevices A, B, and C. Each device was a tube that functioned as anosmotic pump. The tubes were formed from silicone. Each tube defined aninterior reservoir, and a volume of lidocaine was loaded into thereservoir. Each tube also defined an exterior osmotic surface area, andan orifice was formed in the osmotic surface area. The orifice permittedreleasing the lidocaine from the reservoir under osmotic pressure.

More specifically, Device A was a silicone tube having an osmoticsurface area of about 2 cm and a reservoir volume of about 2 mg. DeviceB was a silicone tube having an osmotic surface area of about 1 cm and areservoir volume of about 1 mg. Device C was a silicone tube having anosmotic surface area of about 2 cm, one half of which was covered withtwo polyurethane sheaths near the release orifice, and a reservoirvolume of about 2 mg. Due to the sheaths, the effective osmotic surfacearea of Device C was about the same as the osmotic surface area ofDevice B, and yet the reservoir volume of Device C was about the samevolume as the reservoir volume Device A. For each device, the ends ofthe silicone tube were sealed with micro spheres, and the reservoir wasloaded with lidocaine. In the case of Device C, the sheaths were placedrelatively near the orifice to limit isolation of the lidocaine duringrelease.

The devices were then tested in vitro in water at 37° C., and theresulting release profiles were plotted in FIG. 18. Drug payload(m_(p)), zero-order drug release rate ({dot over (m)}_(z)), and deliverytime scale (m_(p)/{dot over (m)}_(z)) for each device are shown in Table1, as relative values with respect to the values for Device A. BecauseDevice B had a length that was about one half the length of Device A,both the drug payload and the zero order release rate for Device B wereabout half the values of the Device A, which results in the samedelivery time scale for Device A and Device B. FIG. 18 shows thatoverall in vitro release profiles with respect to time were similar forDevice A and Device B. Device C had a length that was about the same asthe length of Device A, but about one half of the length of Device C wascovered with polyurethane sheaths to reduce or minimize waterpermeation. Thus, the zero order release rate for Device C was abouthalf the zero order release rate for Device A. Therefore, the deliverytime scale of Device C was about twice that of Device A. FIG. 18 showsthat the drug release for Device C is twice as slow as that for DeviceA.

TABLE 1 Comparison for three devices marked as A, B, and C shown in FIG.17. Variable Drug payload Zero order release rate Delivery time scaleDevice (m_(p)) ({dot over (m)}_(z)) (m_(p)/{dot over (m)}_(z)) A 1 1 1 B½ ½ 1 C 1 ½ 2

EXAMPLE 3 Selection of Device Characteristics to Achieve a DesiredRelease Rate

Listed below are equations that permit selecting device characteristicsto achieve a desired release rate. More specifically, the equations maypermit determining how much of a device should be covered with a coatingor sheath to achieve a certain release rate for a certain payload. Thedevice characteristics may be determined with reference to a controldevice of control dimensions that releases a control drug payloadaccording to a control release profile during in vitro testing. Oncetheses control parameters are known, the equations may determine thecharacteristics of a target device that exhibits a target release ratein comparison to the control device.

For purposes of example, Device A of FIG. 17 was the control device.Device A had a the following design parameters:

Tube inner diameter: d_(o)=0.3048 mm

Tube wall thickness. h_(o)=0.1651 mm

Tube length: L_(o)=2 cm

Payload: m_(p,o)=2 mg

Treatment duration: about 3 days

A control release rate m_(z,o) for Device A is plotted in FIG. 18.Starting with such parameters on the control device, the equations belowpermit obtaining device characteristics for a target device that willexhibit a desired delivery rate for a desired payload in comparison tothe control device. More specifically, two variables are defined:

a=multiplication factor of the target zero order delivery rate

b=multiplication factors of the target payload, respectively. Thedefinitions yield the desired target condition as follows:

Zero order delivery rate ({dot over (m)}_(z)) a times increase comparedwith the base condition

Drug payload (m_(p)): b times increase compared with the base condition

It is assumed here that drug and tube material remain the same for boththe base condition and the target condition. The parameters for thetarget condition have no subscripts here. The zero-order delivery ratecondition gives

$\begin{matrix}{{\frac{d + h}{h}L_{n}} = {\left( {\frac{d_{o} + h_{o}}{h_{o}}L_{o}} \right)a}} & (1.13)\end{matrix}$

and the drug payload condition gives

d ² L=(d _(o) ² L _(o))b   (1.14)

Tube wall thickness can vary, but here it is fixed for simplicity:

h=h₀   (1.15)

It is noted that a tube wall that is too thin may not have sufficientmechanical integrity while a tube wall that is too thick may experiencean undesirably long induction time for initial drug release from thedevice. Thus, a reasonable range of tube wall thickness may bedetermined based on the mechanical properties and water permeability ofthe material used to form the polymer tube.

A silicone tube with an appropriately thin wall may act as a waterpermeable membrane when a drug is loaded inside the tube. The equationsbelow first consider the case where the water permeable tube is notcovered with a polymer sheath. Device A and Device B in FIG. 18 showsuch a case. Water can permeate into the drug reservoir through theentire length of the tube, and so

L=L_(n)   (1.16)

The quadratic equation for the inner diameter can be obtained from Eq.(1.13) and Eq. (1.14): as:

$\begin{matrix}{{d^{2} - {\frac{\left( {b/a} \right)d_{o}^{2}}{d_{o} + h_{o}}d} - {\frac{\left( {b/a} \right)d_{o}^{2}}{d_{o} + h_{o}}h_{o}}} = 0} & (1.17)\end{matrix}$

where one solution is positive and the other is negative. The positivesolution is designated as d₁, and thus the solution for the tube lengthis

$\begin{matrix}{L_{1} = {\frac{d_{0}^{2}L_{0}b}{d_{1}^{2}} = {\frac{d_{0} + h_{0}}{d_{1} + h_{0}}L_{0}a}}} & (1.18)\end{matrix}$

Thus, the tube inner diameter and tube length can be calculated once themultiplication factors for the delivery rate and the drug payload arechosen. Two examples are shown below in Table 2. For tubes formed fromdifferent polymers or holding other drugs, additional in vitro releasestudies may be performed to obtain base conditions for that specificcombination of polymer tube and drug.

TABLE 2 Specifications for two examples of devices for human applicationMultiplication factor For delivery rate (a): 10 For delivery rate (a):20 Design parameter For payload (b): 50 For payload (b): 200 Tube inner1.1326 mm 2.1303 mm diameter (d₁) Tube length (L₁) 7.2418 cm 8.1885 cmMacro loop 2.3051 cm 2.6065 cm diameter (D₁) Drug payload (m_(p)) 100 mg400 mg Treatment period 15 days 30 days

As mentioned above, the length covered with sheath is denoted as L_(S).The previous section corresponds to the case where L_(S)=0, which isoften the case as it is usually desirable to reduce the diameter of thedevice. For example, omitting the sheath may facilitate inserting thedevice through the working channel of a cystoscope, which may have adiameter of about 2.4 mm of less. Nonetheless, the equations nextconsider the case where the water permeable tube is at least partiallycovered with a material that reduces the water permeability of the tube,meaning L_(S)>0. Device C in FIG. 18 show such a case. The Device C maybe at least partially coated with a sheath or coating made of a polymerhaving a relatively low permeability to water, such as polyurethane,which may reduce or minimize water permeation into the tube. A specialcoating such as parylene may also be used to reduce water permeation.Eq. (1.13) and Eq. (1.14) show that the tube length (L) increases fasterthan the sheath covered length (L_(n)) as the tube inner diameter (d)deceases (L∝1/d² and L_(n)∝1/(d+h)). The length of the portion coveredwith sheath is

L_(S) =L−L _(n)   (1.19)

Using Eq. (1.13), (1.14), and (1.19), the length covered with sheath isexpressed as

$\begin{matrix}{L_{s} = {{\pi \; D} - \frac{\left( {d_{o} + h_{o}} \right)L_{o}a}{{d_{o}\sqrt{\left( {L_{o}b} \right)/\left( {\pi \; D} \right)}} + h_{o}}}} & (1.20)\end{matrix}$

or using Eq. (1.18), the following is obtained

$\begin{matrix}{\frac{L_{s}}{L_{1}} = {\frac{D}{D_{1}} - \frac{d_{1} + h_{o}}{d + h_{o}}}} & (1.21)\end{matrix}$

where subscript 1 indicates the case where no sheath is used. Theportion of the tube length covered with sheath can be expressed in termsof the tube inner diameter (d) as

$\begin{matrix}{\frac{L_{S}}{L} = {1 - {\frac{a\left( {d_{o} + h_{o}} \right)}{{bd}_{o}^{2}}\left( \frac{d^{2}}{d + h_{o}} \right)}}} & (1.22)\end{matrix}$

or in terms of the loop diameter (D) as

$\begin{matrix}{\frac{L_{S}}{L} = {1 - \frac{\left( {d_{o} + h_{o}} \right)L_{o}a}{{d_{o}\sqrt{\pi \; {bL}_{o}D}} + {\pi \; h_{o}D}}}} & (1.23)\end{matrix}$

EXAMPLE 4 Selecting the Characteristics of an Elastic Wire

A compression test was performed on a pretzel-shaped retention frame,shown in FIG. 19, to demonstrate how various design factors affect thespring constant of a retention frame. The pretzel-shaped elastic wirewas made of super-elastic nitinol wire having a diameter of 0.009 inch,or 0.2286 mm. As the compression test was performed, data regardingforce and displacement was collected. This data is plotted on the graphshown in FIG. 20.

As a compressive load was applied to the retention frame, the framedeformed from the shape shown in A to the shape shown in B, and finally,to the shape shown in C. Specifically, the three shapes of the device A,B, and C shown in FIG. 19 correspond to the three data points A, B, andC on the graph in FIG. 20.

As shown in FIG. 19, the compressive force was generally absorbed by alarger, common arch of the pretzel-shaped elastic wire as the framedeformed from shape A and shape B. Once the frame assumed shape B, thetwo semi-circles that make up the elastic wire overlapped. Theforce/displacement plot demonstrates an increase in slope (approximately15 times), which was sustained as the frame deformed from shape B toshape C.

The test and subsequent analysis revealed that a small Young's modulus Efor low modulus elastomers can be compensated for by one or more of thefollowing: by decreasing the radius of the arch, by increasing the wirediameter, and by having multiple and/or overlapped circles or windings.For example, decreasing the radius of an arch formed by the frame by afactor of two (2) and increasing the diameter of the wire used to formthe frame by a factor of two (2) can significantly increase the springconstant by a factor of 2⁷ or 128.

EXAMPLE 5 Sample Spring Constants for Certain Low Modulus Wires

A nitinol wire having a Young's modulus of about 30 GPa, a diameter ofabout 0.2286 mm, an arc radius of about 1.5 cm, and one coil may have aspring constant of about 3.7 N/m. A polyurethane wire having a Young'smodulus of about 25 MPa, a diameter of about 1 mm, an arc radius ofabout 1 cm, and one coil may have a spring constant of about 3.8 N/m. Asilicone wire having a Young's modulus of about 2.41 MPa, a diameter ofabout 1.2 mm, an arc radius of about 0.75 cm, and two coils may have aspring constant of about 3.6 N/m. A poly(glycerol-sebacate) (PGS) wirehaving a Young's modulus of about 1.7 MPa, a diameter of about 1.2 mm,an arc radius of about 0.76 cm, and three coils may have a springconstant of about 3.7 N/m.

EXAMPLE 6 In Vitro Delivery of Lidocaine from Various Devices

An in vitro lidocaine release study was performed with five differentdevices. Each device was a silicone tube loaded with crystallizedlidocaine pieces. Two different sizes of silicone tubes were used.Specifications for the devices are shown in Table 3. Each tube wassealed with stainless steel microballs inserted into the ends. Exceptfor the control device, an orifice was drilled in each tube between themicroballs. Each orifice had a diameter of about 50 μm. The diameter wasselected to obtain a first-order release profile, based on the resultsfrom in vitro release experiments performed with CSC. The devicedesignated Type III in the table has a polyurethane sheath, similar tothe one shown in FIG. 13, to reduce water permeation into the device.The device designated Control in the table did not have an orifice.During the experiment, the microballs were pushed outward due to aninternal buildup of hydrostatic pressure within the tube. In vitrolidocaine release curves for the devices are shown in FIG. 21.

TABLE 3 Specifications for the devices used for in vitro lidocainerelease study Tube wall I.D. × O.D. thickness Total tube Type Payload(inches) (inches) length (cm) I 2 mg 0.012 × 0.025 0.0065 2 II 1 mg0.012 × 0.025 0.0065 1 III 2 mg 0.012 × 0.025 0.0065 2 (half coveredwith sheath) IV 4 mg 0.020 × 0.037 0.0085 2 Control 4 mg 0.020 × 0.0370.0085 2 (no orifice)

EXAMPLE 7 In Vivo Delivery and Retention of Device in Rabbit Bladder

A vesicle retention frame was made of a Nitinol wire (diameter 0.009inch) covered with silicone tubing. Platinum wire was coiled at the tipend of the Nitinol wire, and a biocompatible UV epoxy was applied andcured to fabricate a blunt tip end onto the Nitinol wire. The tips areblunt and soft to avoid possible irritations and scarring of the vesicletissue surface, e.g., the bladder. The coated wire device was in theshape of two overlapping loops with the ends positioned inside of thecircle-like outer perimeter defined by the loops. The vesicle retentionframe was substantially pretzel shaped.

The retention device was implanted into a rabbit bladder by a 10 Fr.urinary catheter. The shape of the device was chosen as the resistanceto the compression increases upon compression of the two loops (i.e.,sub-circles). This spring-like feature was intended to prevent collapseof the structure so that it may not enter the urethra. The deviceimmediately returned to its original shape once the compression wasremoved, due to the superelastic property of Nitinol. Instead ofcompressing the device into a catheter core, the device was uncurled andpushed through the catheter lumen using a stylet. The device curled backinto its original form after emerging from the distal end of thecatheter. The device was not excreted from the bladder.

EXAMPLE 8 In Vivo Delivery of Lidocaine in Rabbit Bladder

Drug exposure studies were performed in vivo in rabbit to investigatethe absorption of lidocaine by the bladder. The study was conducted withmale New Zealand Wite rabbits. Lidocaine was delivered to some of therabbits via intravesically implanted drug delivery devices, whileinstillations were performed on other rabbits for comparative purposes.

For the rabbits treated via instillation, 10 mL of aqueous lidocainesolution was instilled into the bladder. Based on prior clinicalstudies, the lidocaine dose was either 2 mg or 5 mg per kg of bodyweight. The solution was instilled using a 10-Fr pediatric Foleycatheter inserted through the urethra, and the solution was retained inthe bladder for one or two hours. Blood samples were collected atmultiple time points before and after instillation. Bladders werecollected from the rabbits one day after instillation, and urine sampleswere also collected at that time.

Rabbits treated via intravesical implant received either a “three-day”device or a “six-day” device. Both devices were comparable in form tothe device shown in FIG. 1, each having a pretzel shaped retention frameassociated with a silicone drug reservoir component. The drug reservoircomponent of the three-day device had a length of about 0.0065 inches,an inner diameter of about 0.012 inches, an outer diameter of about0.025 inches, and a drug load of about 2 mg of lidocaine, while the drugreservoir component of the six-day device had a length of about 0.0085inches, an inner diameter of about 0.020 inches, an outer diameter ofabout 0.037 inches, and a drug load of about 2 mg of lidocaine. Theterms “three-day device” and “six-day device” refer to the configurationof the device and not the length of implantation. For each rabbit, thedevice was inserted via a modified 10 Fr. urethral catheter using theprocedure described above with reference to FIG. 16. The catheter wasremoved after the device was implanted. Blood samples were collected atmultiple points before and after the device implantation. Additionally,x-ray images were taken for one rabbit immediately after implantation,two days after implantation, and nine days after implantation, in boththe right lateral recumbent position and the supine position. Multiplex-ray images taken at different times revealed that the device movedfreely within the bladder rather than staying in one position. Thedevice was well tolerated by the rabbits over the course of the in vivostudy without any health problems. Bladders were collected from therabbits at multiple time points after implantation, including one day,two days, three days, and six days. Urine samples were also collected atthe time the bladders were removed.

The blood, bladder and urine samples were analyzed to determine thelidocaine concentration in plasma, bladder tissue, and urine. FIG. 22 isa graph illustrating lidocaine plasma concentration over time for thevarious treatments, and FIG. 23 is the same graph with the x-axismodified. In these graphs, instillation treatments are shown with dottedlines and the device treatments are shown with solid lines. The keyindicates the weight of each rabbit along with the treatment type. Thedata presentation in FIG. 22 generally permits comparing the variousinstillation treatments to the various intravesical implant treatments,while the data presentation in FIG. 23 generally permits comparing thevarious intravesical implant treatments to each other.

As shown in FIG. 22, instillation of the lidocaine solution resulted inan initial surge of lidocaine plasma concentration, but lidocaine was nolonger detected in the plasma after one day. Thus, instillationtreatment permits a sudden increase in lidocaine plasma concentration,but this increase is quickly followed by a rapid decline. In the case ofthe rabbit treated via instillation of a 5 mg/kg lidocaine solution fortwo hours, the peak plasma concentration exceeded 100 ng/mL, which iswithin the known toxicity limit of lidocaine by a factor of ten.However, such high initial peak concentrations may be necessary toprovide relief between repeated instillations, eventhough systemicallyundesirable.

FIG. 22 also shows that lidocaine plasma concentration was relativelylower in rabbits treated with the implanted device than in rabbitstreated via instillation. However, the rabbits treated with theimplanted device maintained a relatively higher lidocaine plasmaconcentration with the passage of time.

FIG. 23 shows that release from the three-day device slowed after twelvehours, which is consistent with the results obtained in the in vitrorelease study of Example 6. The six-day device, which had twice thepayload of the three-day device, demonstrated a more extended releaseprofile. However, the six-day device demonstrated an initial inductiontime, which is consistent with the results obtained in the in vitrorelease study of Example 6. The induction time is attributable to thethicker tube used for the six-day device, which is hydrated over theinduction time to initiate lidocaine release from the device. All inall, the results show that the delivery of a depot of lidocaine via animplanted device, when compared to delivery via instillation, may permitmaintaining relatively higher lidocaine plasma concentrations with thepassage of time while avoiding high peak lidocaine plasmaconcentrations.

Because the target site for intravesical treatment is bladder tissue,the bladder tissue concentration of lidocaine is a more direct index ofthe efficacy of treatment via an intravesical implant than the plasmaconcentration. FIG. 24 shows lidocaine concentration in bladder tissueover time for various treatments via intravesical implant. Lidocainetissue concentrations are shown for a three-day device at multiple timepoints after implantation, including one day after implantation, twodays after implantation, and three days after implantation In otherwords, the device was not necessarily retained in the bladder for threedays. Lidocaine tissue concentrations are also shown for a six-daydevice at the time point of six days after implantation. As shown, thethree-day device exhibited decreasing lidocaine tissue concentrationover the course of three days, while the six day device exhibitedlidocaine tissue concentrations after six days that compared to thelidocaine tissue concentrations exhibited by the three-day device afterone day. Lidocaine tissue concentrations were also measured one dayafter intravesical instillation, but the tissue concentration was belowthe level of detection. It also should be noted that the lidocainetissue concentration is on the order of micrograms per gram of tissue.

FIG. 25 shows the correlation between lidocaine plasma concentration andlidocaine tissue concentration for the intravesical implantsCorrelations are also shown for the instillation treatments one dayafter instillation, but these concentrations are negligible incomparison with the device treatments. As shown, higher lidocaine plasmaconcentrations are generally associated with higher lidocaine tissueconcentrations. However, the lidocaine tissue concentrations areapproximately one thousand times higher than the lidocaine plasmaconcentration. Therefore, delivery of a depot of lidocaine via animplanted device may provide higher drug exposure to the bladder tissuewhile avoiding the high peak plasma concentration.

Lidocaine urine concentration was also measured for two animals thatwere treated with the three-day device and six-day device, respectively.The results are shown in FIG. 26. Bladder tissue and urine samples werecollected three days after implantation for the rabbit that received thethree-day device and six days after implantation for the rabbit thatreceived the six-day device. As shown, the order of magnitude of thelidocaine urine concentration was comparable to the lidocaine tissueconcentration, which comports with in vitro studies described below withreference to Example 9 and FIG. 27, below.

EXAMPLE 9 In Vitro Absorption of Lidocaine in Rat Bladder

A study was performed on rat bladders in vitro to investigate the effectof pH and time on lidocaine absorption into the urothelium of thebladder. A number of different lidocaine solutions were made fromartificial urine and radiolabeled lidocaine. Each lidocaine solution hada lidocaine concentration of either 10⁻⁵% (10⁻⁴ mg/mL) or 1% (10 mg/mL),and a pH ranging from 4.0 to 8.5.

Rat bladders were inverted to expose the urothelium or inner lining ofthe bladder. The inverted bladders were placed in the lidocainesolutions, each lidocaine solutions having a different concentration andpH. The bladders were incubated in the lidocaine solutions for one ofthe following amounts of time: ten minutes, one hour, one day, threedays or five days. After the designated incubation time expired, eachbladder was removed from the lidocaine solution and the lidocaineconcentration in the in the tissue was determined.

FIG. 27 is a graph illustrating the effect of pH on the absorption oflidocaine solution in vitro into the tissue of rat bladder, for timeperiods of one hour and for one day. The graph pertains to the lidocainesolution having a 1% lidocaine concentration only. As shown, the pH ofthe lidocaine solution slightly affected the absorption of lidocaineinto the bladder tissue after one hour, but the pH did not significantlyaffect lidocaine absorption after one day. For each bladder, the plateautissue concentration (or absorbed lidocaine mass per bladder tissuemass) was about 10000 mg/kg or 1%, which was the lidocaine concentrationof the lidocaine solution in which the bladder was immersed. This resultimplies that the topical absorption of lidocaine into the bladder overan extended time period can be independent of the pH of the lidocainesolution. This result also indicates that buffering the lidocainesolution may not be necessary for topical absorption of lidocaine by theurothelium via long term in vivo exposure in the bladder.

FIG. 28 is a graph illustrating lidocaine tissue concentration overtime, exhibited during studies performed in vitro on rat bladder with10⁻⁵% and 1% lidocaine solutions of varying pH. The graph shows theeffect of lidocaine concentration and pH on the absorption of lidocaineinto rat bladder tissue over time. Results for lidocaine solutionshaving 10⁻⁵% concentration are plotted separately from those having 1%concentration. As shown, lidocaine tissue concentration increasesquickly (within about ten minutes) and reach a plateau for both 10⁻⁵%and 1% lidocaine solutions. As shown, the plateau lidocaine tissueconcentration for the 10⁻⁵% lidocaine solution is in the order of 0.1mg/kg or 10⁻⁵%, while he plateau lidocaine tissue concentration for the1% lidocaine solution is in the order of 10000 mg/kg or 1%. This resultshows that the partition coefficient for lidocaine tissue to lidocainesolution is about unity for in vitro lidocaine absorption intourothelium. Higher lidocaine concentration shows higher lidocaineabsorption into urothelium.

Publications cited herein and the materials for which they are cited arespecifically incorporated by reference. Modifications and variations ofthe methods and devices described herein will be obvious to thoseskilled in the art from the foregoing detailed description. Suchmodifications and variations are intended to come within the scope ofthe appended claims.

1. An implantable medical device for controlled drug deliverycomprising: at least one drug reservoir component comprising a drug; anda vesicle retention frame which comprises an elastic wire having a firstend, an opposing second end, and an intermediate region therebetween,wherein the drug reservoir component is attached to the intermediateregion of the vesicle retention frame.
 2. The device of claim 1, whereinthe elastic wire has a spring constant between 3 N/m and 60 N/m.
 3. Thedevice of claim 2, wherein the elastic wire has a spring constantbetween about 3.6 N/m and about 3.8 N/m.
 4. The device of claim 1,wherein the elastic wire comprises a low modulus elastomer.
 5. Thedevice of claim 4, wherein the low modulus elastomer comprises silicone,polyurethane, styrenic thermoplastic elastomer, orpoly(glycerol-sebacate).
 6. The device of claim 1, wherein the elasticwire comprises a biocompatible nickel-titanium alloy, atitanium-molybdenum alloy, or another superelastic alloy or shape memorymaterial.
 7. The device of claim 1, wherein the elastic wire has anuncompressed state which is curled in the form of two or more loops. 8.The device of claim 7, wherein the first and second ends of the elasticwire are bounded within said one or more loops.
 9. The device of claim1, wherein the drug reservoir component comprises (i) at least oneelongated elastomeric tube having a first end portion and an opposingsecond end portion, and (ii) a drug contained within said elastomerictube, said tube being operable in vivo to dispense the drug at acontrolled rate.
 10. The device of claim 9, wherein the elastomeric tubeis formed of a water permeable silicone or other water permeablematerial.
 11. The device of claim 9, wherein the elastomeric tubecontrols release of the drug by osmosis, diffusion, or a combinationthereof.
 12. The device of claim 9, wherein the elastomeric tubecontrols release of the drug by osmosis.
 13. The device of claim 11,wherein the elastomeric tube comprises one or more apertures fordispensing the drug at a controlled rate.
 14. The device of claim 13,wherein each of the one or more apertures is circular and has a diameterbetween about 25 μm and about 500 μm.
 15. The device of claim 9, whereinthe elastomeric tube is cylindrical with an inner diameter between about0.3 mm and about 2 mm and an outer diameter between about 0.6 mm andabout 3 mm.
 16. The device of claim 9, wherein the drug is in a drugformulation core disposed within a central channel in the elastomerictube.
 17. The device of claim 16, wherein the drug formulation is in asolid or semi-solid form.
 18. The device of claim 9, wherein theelastomeric tube comprises a composite of a bioresorbable matrixmaterial and the drug.
 19. The device of claim 1, wherein the drugcomprises a local anesthetic agent, heparin, sodium hyaluronate,glycosaminoglycans, dimethyl sulfoxide, oxybutynin, mitomycin C,flavoxate, pentosan polysulfate sodium, or a combination thereof. 20.The device of claim 1, wherein the drug comprises a local anestheticagent is a salt of an aminoamide or a salt of an aminoester.
 21. Thedevice of claim 20, wherein the drug comprises lidocaine, prilocaine,mepivacaine, ropivacaine, benzocaine, procaine, proparacaine,tetracaine, bupivacaine, or a combination thereof.
 22. The device ofclaim 1, which is resorbable in vivo.
 23. The device of claim 1, whereinthe drug reservoir portion comprises: a first end attached to a firstlocation on the intermediate region of the vesicle retention frame; anda second end attached to a second location on the intermediate region ofthe vesicle retention frame.
 24. The device of claim 1, wherein the drugreservoir portion comprises a central portion between the first end andthe second end, the central portion being unattached to the vesicleretention frame.
 25. The device of claim 1, wherein the drug reservoirportion is substantially aligned with the vesicle retention frame alongat least the intermediate region.
 26. The device of claim 1, wherein thedevice comprises at least two drug reservoir portions substantiallyaligned with the vesicle retention frame along at least the intermediateregion.
 27. An implantable medical device for controlled drug deliverycomprising: at least one drug reservoir component which comprises anelongated, water permeable, elastomeric tube having a first end and anopposing second end, a solid or semi-solid drug formulation core withinthe tube, wherein the tube dispenses the drug in vivo at a controlledrate; and a vesicle retention frame which comprises an elastic wirehaving a first end, an opposing second end, and an intermediate regiontherebetween, wherein the elastic wire comprises a low modulus elastomeror a superelastic alloy, wherein the elastomeric silicone tube of thedrug reservoir component is attached to the vesicle retention frameabout the intermediate region.
 28. The device of claim 27, which has ahigh profile form in which the elastic wire is curled into two or moreloops incapable of passing through a lumen of a catheter and a lowprofile form in which the device is capable of passing through saidcatheter lumen.
 29. The device of claim 27, wherein the elastic wire hasa spring constant between 3 N/m and 60 N/m.
 30. The device of claim 27,wherein the elastomeric tube has an aperture through which the drug canbe released in vivo at an osmotically controlled rate.
 31. The device ofclaim 30, wherein the elastic wire has a spring constant between about3.6 N/m and about 3.8 N/m.
 32. The device of claim 27, wherein the lowmodulus elastomer comprises silicone, polyurethane, a styrenicthermoplastic elastomer, or poly(glycerol-sebacate).
 33. The device ofclaim 27, wherein the drug formulation comprises a local anestheticagent.
 34. The device of claim 27, wherein the elastomeric tube has anexterior osmotic surface, and an orifice formed through the osmoticsurface for communicating a drug from the reservoir; and a coating orsheath covering at least a portion of the osmotic surface to reduce thepermeability of the osmotic surface.
 35. A method for administration ofa drug into a patient's bladder, comprising: providing a lumen device,which has a distal end, an opposing proximal end, and an open lumenextending therebetween; inserting the distal end of the lumen deviceinto the bladder of a patient in need of treatment, where the proximalend of the lumen device remains outside of the patient; deforming thedevice of claim 1 and passing it into the proximal end of the lumen ofthe lumen device; driving the deformed device through the lumen and outof the lumen, whereupon the device returns to its undeformed shape forretention in the bladder; removing the lumen device from the patient;and releasing the drug from said device of claim
 1. 36. The method ofclaim 35, wherein the patient is in need of treatment for interstitialcystitis, overactive bladder syndrome, or bladder cancer.
 37. Animplantable medical device for controlled drug delivery comprising: atube formed of a water permeable material and comprising an interiorreservoir, an exterior osmotic surface, and an orifice formed throughthe osmotic surface for communicating a drug from the reservoir; and acoating or sheath covering at least a portion of the osmotic surface toreduce the permeability of the osmotic surface.
 38. The device of claim37, wherein the water permeable material comprises a silicone and thecoating or sheath comprises a polyurethane.
 39. The device of claim 37,wherein the coating or sheath is relatively less permeable to water thanthe water permeable material forming the tube.
 40. The device of claim37, wherein the tube comprises two reservoirs, and wherein at least onecharacteristic of the coating or sheath varies along the tube to achievedifferent release rates from the two reservoirs.
 41. The device of claim40, wherein the at least one characteristic of the coating or sheath isselected from the group consisting of: the thickness of the coating orsheath, the size of the coating or sheath, the shape of the coating orsheath, the position of the coating or sheath on the tube, the locationof the coating or sheath on the tube, the orientation of the coating orsheath on the tube, and the material used to form the coating or sheath.42. The device of claim 37, wherein the coating or sheath is spacedinward from an end of the tube, such that a portion of the tube adjacentto the end is not covered by the coating or sheath.
 43. The device ofclaim 37, wherein the coating or sheath is positioned about the tube inclose proximity to the orifice.
 44. The device of claim 37, furthercomprising a vesicle retention frame associated with the tube.
 45. Amethod of treatment of the bladder in a patient, the method comprising:implanting wholly within the patient's bladder a drug release device;and controllably releasing a local anesthetic agent from the drugdelivery device in a manner providing a sustained, therapeuticallyeffective concentration of the anesthetic agent in the urothelium of thebladder, while avoiding high peak plasma concentrations of theanesthetic agent.
 46. The method of claim 45, wherein the anestheticagent comprises lidocaine.
 47. The method of claim 45, wherein theconcentration of the anesthetic agent in the urothelium is at least 1000times higher than the plasma concentration.
 48. The method of claim 45,wherein the therapeutically effective concentration of the anestheticagent in the urothelium is sustained for between 1 and 30 days.
 49. Amethod of treatment of the bladder in a patient, the method comprising:implanting wholly within the patient's bladder a drug release device;and controllably releasing a drug from the drug delivery device in amanner providing a sustained, therapeutically effective concentration ofthe drug in the urothelium of the bladder, while avoiding high peakplasma concentrations of the anesthetic agent, wherein the drug has ahalf-life that is equivalent to or within 25% of that of lidocaine.